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Use static allocas for temporaries. (#5734)

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Previously we created allocas for temporaries at whatever point in the
output LLVM function we'd reached. This would result in these being
dynamic allocas (performing a dynamic stack allocation), which is
inefficent and can lead to a stack overflow if it happens in a loop.

Switch to putting the allocas in the entry block instead, and instead
generate a lifetime start marker when we reach the point where the
temporary is introduced. We already did this for local variables; this
is just factoring out and reusing that code.
This commit is contained in:
Richard Smith
2025-06-25 21:53:39 +00:00
committed by GitHub
parent 3585b31813
commit a556cf41fc
16 changed files with 286 additions and 176 deletions
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toolchain/lower/testdata/function/generic/call_basic.carbon
Vendored
+61 -59
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@@ -99,26 +99,27 @@ fn M() {
// CHECK:STDOUT: %ptr_f64.var = alloca ptr, align 8, !dbg !27
// CHECK:STDOUT: %ptr_i8.var = alloca ptr, align 8, !dbg !28
// CHECK:STDOUT: %c.var = alloca {}, align 8, !dbg !29
// CHECK:STDOUT: %H.call.loc25 = call i32 @_CH.Main.b88d1103f417c6d4(i32 %x), !dbg !30
// CHECK:STDOUT: %H.call.loc26 = call %type @_CH.Main.5754c7a55c7cbe4a(%type zeroinitializer), !dbg !31
// CHECK:STDOUT: %H.call.loc27 = call %type @_CH.Main.5754c7a55c7cbe4a(%type zeroinitializer), !dbg !32
// CHECK:STDOUT: %G.call = call i32 @_CG.Main.b88d1103f417c6d4(i32 %x), !dbg !33
// CHECK:STDOUT: %H.call.loc28 = call i32 @_CH.Main.b88d1103f417c6d4(i32 %G.call), !dbg !34
// CHECK:STDOUT: %.loc40_6.1.temp = alloca {}, align 8, !dbg !30
// CHECK:STDOUT: %H.call.loc25 = call i32 @_CH.Main.b88d1103f417c6d4(i32 %x), !dbg !31
// CHECK:STDOUT: %H.call.loc26 = call %type @_CH.Main.5754c7a55c7cbe4a(%type zeroinitializer), !dbg !32
// CHECK:STDOUT: %H.call.loc27 = call %type @_CH.Main.5754c7a55c7cbe4a(%type zeroinitializer), !dbg !33
// CHECK:STDOUT: %G.call = call i32 @_CG.Main.b88d1103f417c6d4(i32 %x), !dbg !34
// CHECK:STDOUT: %H.call.loc28 = call i32 @_CH.Main.b88d1103f417c6d4(i32 %G.call), !dbg !35
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(i64 8, ptr %var_f64.var), !dbg !25
// CHECK:STDOUT: %.loc32 = load double, ptr %var_f64.var, align 8, !dbg !35
// CHECK:STDOUT: %H.call.loc32 = call double @_CH.Main.66be507887ceee78(double %.loc32), !dbg !36
// CHECK:STDOUT: %.loc32 = load double, ptr %var_f64.var, align 8, !dbg !36
// CHECK:STDOUT: %H.call.loc32 = call double @_CH.Main.66be507887ceee78(double %.loc32), !dbg !37
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(i64 8, ptr %ptr_i32.var), !dbg !26
// CHECK:STDOUT: %.loc34 = load ptr, ptr %ptr_i32.var, align 8, !dbg !37
// CHECK:STDOUT: %H.call.loc34 = call ptr @_CH.Main.e8193710fd35b608(ptr %.loc34), !dbg !38
// CHECK:STDOUT: %.loc34 = load ptr, ptr %ptr_i32.var, align 8, !dbg !38
// CHECK:STDOUT: %H.call.loc34 = call ptr @_CH.Main.e8193710fd35b608(ptr %.loc34), !dbg !39
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(i64 8, ptr %ptr_f64.var), !dbg !27
// CHECK:STDOUT: %.loc36 = load ptr, ptr %ptr_f64.var, align 8, !dbg !39
// CHECK:STDOUT: %H.call.loc36 = call ptr @_CH.Main.e8193710fd35b608(ptr %.loc36), !dbg !40
// CHECK:STDOUT: %.loc36 = load ptr, ptr %ptr_f64.var, align 8, !dbg !40
// CHECK:STDOUT: %H.call.loc36 = call ptr @_CH.Main.e8193710fd35b608(ptr %.loc36), !dbg !41
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(i64 8, ptr %ptr_i8.var), !dbg !28
// CHECK:STDOUT: %.loc38 = load ptr, ptr %ptr_i8.var, align 8, !dbg !41
// CHECK:STDOUT: %H.call.loc38 = call ptr @_CH.Main.e8193710fd35b608(ptr %.loc38), !dbg !42
// CHECK:STDOUT: %.loc38 = load ptr, ptr %ptr_i8.var, align 8, !dbg !42
// CHECK:STDOUT: %H.call.loc38 = call ptr @_CH.Main.e8193710fd35b608(ptr %.loc38), !dbg !43
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(i64 0, ptr %c.var), !dbg !29
// CHECK:STDOUT: %.loc40_6.1.temp = alloca {}, align 8, !dbg !43
// CHECK:STDOUT: call void @_CH.Main.15b1f98bd9cc0c5b(ptr %.loc40_6.1.temp, ptr %c.var), !dbg !43
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(i64 0, ptr %.loc40_6.1.temp), !dbg !30
// CHECK:STDOUT: call void @_CH.Main.15b1f98bd9cc0c5b(ptr %.loc40_6.1.temp, ptr %c.var), !dbg !30
// CHECK:STDOUT: ret i32 %x, !dbg !44
// CHECK:STDOUT: }
// CHECK:STDOUT:
@@ -134,26 +135,27 @@ fn M() {
// CHECK:STDOUT: %ptr_f64.var = alloca ptr, align 8, !dbg !50
// CHECK:STDOUT: %ptr_i8.var = alloca ptr, align 8, !dbg !51
// CHECK:STDOUT: %c.var = alloca {}, align 8, !dbg !52
// CHECK:STDOUT: %H.call.loc25 = call double @_CH.Main.66be507887ceee78(double %x), !dbg !53
// CHECK:STDOUT: %H.call.loc26 = call %type @_CH.Main.5754c7a55c7cbe4a(%type zeroinitializer), !dbg !54
// CHECK:STDOUT: %H.call.loc27 = call %type @_CH.Main.5754c7a55c7cbe4a(%type zeroinitializer), !dbg !55
// CHECK:STDOUT: %G.call = call double @_CG.Main.66be507887ceee78(double %x), !dbg !56
// CHECK:STDOUT: %H.call.loc28 = call double @_CH.Main.66be507887ceee78(double %G.call), !dbg !57
// CHECK:STDOUT: %.loc40_6.1.temp = alloca {}, align 8, !dbg !53
// CHECK:STDOUT: %H.call.loc25 = call double @_CH.Main.66be507887ceee78(double %x), !dbg !54
// CHECK:STDOUT: %H.call.loc26 = call %type @_CH.Main.5754c7a55c7cbe4a(%type zeroinitializer), !dbg !55
// CHECK:STDOUT: %H.call.loc27 = call %type @_CH.Main.5754c7a55c7cbe4a(%type zeroinitializer), !dbg !56
// CHECK:STDOUT: %G.call = call double @_CG.Main.66be507887ceee78(double %x), !dbg !57
// CHECK:STDOUT: %H.call.loc28 = call double @_CH.Main.66be507887ceee78(double %G.call), !dbg !58
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(i64 8, ptr %var_f64.var), !dbg !48
// CHECK:STDOUT: %.loc32 = load double, ptr %var_f64.var, align 8, !dbg !58
// CHECK:STDOUT: %H.call.loc32 = call double @_CH.Main.66be507887ceee78(double %.loc32), !dbg !59
// CHECK:STDOUT: %.loc32 = load double, ptr %var_f64.var, align 8, !dbg !59
// CHECK:STDOUT: %H.call.loc32 = call double @_CH.Main.66be507887ceee78(double %.loc32), !dbg !60
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(i64 8, ptr %ptr_i32.var), !dbg !49
// CHECK:STDOUT: %.loc34 = load ptr, ptr %ptr_i32.var, align 8, !dbg !60
// CHECK:STDOUT: %H.call.loc34 = call ptr @_CH.Main.e8193710fd35b608(ptr %.loc34), !dbg !61
// CHECK:STDOUT: %.loc34 = load ptr, ptr %ptr_i32.var, align 8, !dbg !61
// CHECK:STDOUT: %H.call.loc34 = call ptr @_CH.Main.e8193710fd35b608(ptr %.loc34), !dbg !62
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(i64 8, ptr %ptr_f64.var), !dbg !50
// CHECK:STDOUT: %.loc36 = load ptr, ptr %ptr_f64.var, align 8, !dbg !62
// CHECK:STDOUT: %H.call.loc36 = call ptr @_CH.Main.e8193710fd35b608(ptr %.loc36), !dbg !63
// CHECK:STDOUT: %.loc36 = load ptr, ptr %ptr_f64.var, align 8, !dbg !63
// CHECK:STDOUT: %H.call.loc36 = call ptr @_CH.Main.e8193710fd35b608(ptr %.loc36), !dbg !64
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(i64 8, ptr %ptr_i8.var), !dbg !51
// CHECK:STDOUT: %.loc38 = load ptr, ptr %ptr_i8.var, align 8, !dbg !64
// CHECK:STDOUT: %H.call.loc38 = call ptr @_CH.Main.e8193710fd35b608(ptr %.loc38), !dbg !65
// CHECK:STDOUT: %.loc38 = load ptr, ptr %ptr_i8.var, align 8, !dbg !65
// CHECK:STDOUT: %H.call.loc38 = call ptr @_CH.Main.e8193710fd35b608(ptr %.loc38), !dbg !66
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(i64 0, ptr %c.var), !dbg !52
// CHECK:STDOUT: %.loc40_6.1.temp = alloca {}, align 8, !dbg !66
// CHECK:STDOUT: call void @_CH.Main.15b1f98bd9cc0c5b(ptr %.loc40_6.1.temp, ptr %c.var), !dbg !66
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(i64 0, ptr %.loc40_6.1.temp), !dbg !53
// CHECK:STDOUT: call void @_CH.Main.15b1f98bd9cc0c5b(ptr %.loc40_6.1.temp, ptr %c.var), !dbg !53
// CHECK:STDOUT: ret double %x, !dbg !67
// CHECK:STDOUT: }
// CHECK:STDOUT:
@@ -183,7 +185,7 @@ fn M() {
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; uselistorder directives
// CHECK:STDOUT: uselistorder ptr @llvm.lifetime.start.p0, { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 13, 12, 11, 10 }
// CHECK:STDOUT: uselistorder ptr @llvm.lifetime.start.p0, { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 15, 14, 13, 12 }
// CHECK:STDOUT: uselistorder ptr @_CH.Main.b88d1103f417c6d4, { 1, 0 }
// CHECK:STDOUT: uselistorder ptr @_CH.Main.5754c7a55c7cbe4a, { 3, 2, 1, 0 }
// CHECK:STDOUT: uselistorder ptr @_CH.Main.66be507887ceee78, { 3, 2, 1, 0 }
@@ -225,20 +227,20 @@ fn M() {
// CHECK:STDOUT: !27 = !DILocation(line: 35, column: 3, scope: !24)
// CHECK:STDOUT: !28 = !DILocation(line: 37, column: 3, scope: !24)
// CHECK:STDOUT: !29 = !DILocation(line: 39, column: 3, scope: !24)
// CHECK:STDOUT: !30 = !DILocation(line: 25, column: 3, scope: !24)
// CHECK:STDOUT: !31 = !DILocation(line: 26, column: 3, scope: !24)
// CHECK:STDOUT: !32 = !DILocation(line: 27, column: 3, scope: !24)
// CHECK:STDOUT: !33 = !DILocation(line: 28, column: 5, scope: !24)
// CHECK:STDOUT: !34 = !DILocation(line: 28, column: 3, scope: !24)
// CHECK:STDOUT: !35 = !DILocation(line: 32, column: 5, scope: !24)
// CHECK:STDOUT: !36 = !DILocation(line: 32, column: 3, scope: !24)
// CHECK:STDOUT: !37 = !DILocation(line: 34, column: 5, scope: !24)
// CHECK:STDOUT: !38 = !DILocation(line: 34, column: 3, scope: !24)
// CHECK:STDOUT: !39 = !DILocation(line: 36, column: 5, scope: !24)
// CHECK:STDOUT: !40 = !DILocation(line: 36, column: 3, scope: !24)
// CHECK:STDOUT: !41 = !DILocation(line: 38, column: 5, scope: !24)
// CHECK:STDOUT: !42 = !DILocation(line: 38, column: 3, scope: !24)
// CHECK:STDOUT: !43 = !DILocation(line: 40, column: 3, scope: !24)
// CHECK:STDOUT: !30 = !DILocation(line: 40, column: 3, scope: !24)
// CHECK:STDOUT: !31 = !DILocation(line: 25, column: 3, scope: !24)
// CHECK:STDOUT: !32 = !DILocation(line: 26, column: 3, scope: !24)
// CHECK:STDOUT: !33 = !DILocation(line: 27, column: 3, scope: !24)
// CHECK:STDOUT: !34 = !DILocation(line: 28, column: 5, scope: !24)
// CHECK:STDOUT: !35 = !DILocation(line: 28, column: 3, scope: !24)
// CHECK:STDOUT: !36 = !DILocation(line: 32, column: 5, scope: !24)
// CHECK:STDOUT: !37 = !DILocation(line: 32, column: 3, scope: !24)
// CHECK:STDOUT: !38 = !DILocation(line: 34, column: 5, scope: !24)
// CHECK:STDOUT: !39 = !DILocation(line: 34, column: 3, scope: !24)
// CHECK:STDOUT: !40 = !DILocation(line: 36, column: 5, scope: !24)
// CHECK:STDOUT: !41 = !DILocation(line: 36, column: 3, scope: !24)
// CHECK:STDOUT: !42 = !DILocation(line: 38, column: 5, scope: !24)
// CHECK:STDOUT: !43 = !DILocation(line: 38, column: 3, scope: !24)
// CHECK:STDOUT: !44 = !DILocation(line: 42, column: 3, scope: !24)
// CHECK:STDOUT: !45 = distinct !DISubprogram(name: "F", linkageName: "_CF.Main.66be507887ceee78", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
// CHECK:STDOUT: !46 = !DILocation(line: 15, column: 1, scope: !45)
@@ -248,20 +250,20 @@ fn M() {
// CHECK:STDOUT: !50 = !DILocation(line: 35, column: 3, scope: !47)
// CHECK:STDOUT: !51 = !DILocation(line: 37, column: 3, scope: !47)
// CHECK:STDOUT: !52 = !DILocation(line: 39, column: 3, scope: !47)
// CHECK:STDOUT: !53 = !DILocation(line: 25, column: 3, scope: !47)
// CHECK:STDOUT: !54 = !DILocation(line: 26, column: 3, scope: !47)
// CHECK:STDOUT: !55 = !DILocation(line: 27, column: 3, scope: !47)
// CHECK:STDOUT: !56 = !DILocation(line: 28, column: 5, scope: !47)
// CHECK:STDOUT: !57 = !DILocation(line: 28, column: 3, scope: !47)
// CHECK:STDOUT: !58 = !DILocation(line: 32, column: 5, scope: !47)
// CHECK:STDOUT: !59 = !DILocation(line: 32, column: 3, scope: !47)
// CHECK:STDOUT: !60 = !DILocation(line: 34, column: 5, scope: !47)
// CHECK:STDOUT: !61 = !DILocation(line: 34, column: 3, scope: !47)
// CHECK:STDOUT: !62 = !DILocation(line: 36, column: 5, scope: !47)
// CHECK:STDOUT: !63 = !DILocation(line: 36, column: 3, scope: !47)
// CHECK:STDOUT: !64 = !DILocation(line: 38, column: 5, scope: !47)
// CHECK:STDOUT: !65 = !DILocation(line: 38, column: 3, scope: !47)
// CHECK:STDOUT: !66 = !DILocation(line: 40, column: 3, scope: !47)
// CHECK:STDOUT: !53 = !DILocation(line: 40, column: 3, scope: !47)
// CHECK:STDOUT: !54 = !DILocation(line: 25, column: 3, scope: !47)
// CHECK:STDOUT: !55 = !DILocation(line: 26, column: 3, scope: !47)
// CHECK:STDOUT: !56 = !DILocation(line: 27, column: 3, scope: !47)
// CHECK:STDOUT: !57 = !DILocation(line: 28, column: 5, scope: !47)
// CHECK:STDOUT: !58 = !DILocation(line: 28, column: 3, scope: !47)
// CHECK:STDOUT: !59 = !DILocation(line: 32, column: 5, scope: !47)
// CHECK:STDOUT: !60 = !DILocation(line: 32, column: 3, scope: !47)
// CHECK:STDOUT: !61 = !DILocation(line: 34, column: 5, scope: !47)
// CHECK:STDOUT: !62 = !DILocation(line: 34, column: 3, scope: !47)
// CHECK:STDOUT: !63 = !DILocation(line: 36, column: 5, scope: !47)
// CHECK:STDOUT: !64 = !DILocation(line: 36, column: 3, scope: !47)
// CHECK:STDOUT: !65 = !DILocation(line: 38, column: 5, scope: !47)
// CHECK:STDOUT: !66 = !DILocation(line: 38, column: 3, scope: !47)
// CHECK:STDOUT: !67 = !DILocation(line: 42, column: 3, scope: !47)
// CHECK:STDOUT: !68 = distinct !DISubprogram(name: "H", linkageName: "_CH.Main.b88d1103f417c6d4", scope: null, file: !3, line: 18, type: !5, spFlags: DISPFlagDefinition, unit: !2)
// CHECK:STDOUT: !69 = !DILocation(line: 19, column: 3, scope: !68)