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Ensure that all allocas are created in the entry block. (#4685)

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Non-entry-block allocas will allocate new stack memory each time they're
reached, resulting in leaking stack memory over time for allocas in a
loop. Move all such allocas to the entry block instead, and use an LLVM
intrinsic to mark when the lifetime of the variable actually begins.
This commit is contained in:
Richard Smith
2024-12-17 00:55:06 +00:00
committed by GitHub
parent 3645143e27
commit c04d62a7d1
44 changed files with 803 additions and 382 deletions
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toolchain/lower/testdata/pointer/pointer_to_pointer.carbon
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+27 -18
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@@ -21,18 +21,29 @@ fn F(p: i32**) -> i32 {
// CHECK:STDOUT: define i32 @_CF.Main(ptr %p) !dbg !4 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: %a.var = alloca ptr, align 8, !dbg !7
// CHECK:STDOUT: %b.var = alloca ptr, align 8, !dbg !7
// CHECK:STDOUT: %c.var = alloca ptr, align 8, !dbg !7
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(i64 8, ptr %a.var), !dbg !7
// CHECK:STDOUT: store ptr %p, ptr %a.var, align 8, !dbg !8
// CHECK:STDOUT: %b.var = alloca ptr, align 8, !dbg !9
// CHECK:STDOUT: %.loc13_17.2 = load ptr, ptr %p, align 8, !dbg !10
// CHECK:STDOUT: store ptr %.loc13_17.2, ptr %b.var, align 8, !dbg !11
// CHECK:STDOUT: %c.var = alloca ptr, align 8, !dbg !12
// CHECK:STDOUT: store ptr %b.var, ptr %c.var, align 8, !dbg !13
// CHECK:STDOUT: %.loc15_12 = load ptr, ptr %c.var, align 8, !dbg !14
// CHECK:STDOUT: %.loc15_11.2 = load ptr, ptr %.loc15_12, align 8, !dbg !15
// CHECK:STDOUT: %.loc15_10.2 = load i32, ptr %.loc15_11.2, align 4, !dbg !16
// CHECK:STDOUT: ret i32 %.loc15_10.2, !dbg !17
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(i64 8, ptr %b.var), !dbg !7
// CHECK:STDOUT: %.loc13_17.2 = load ptr, ptr %p, align 8, !dbg !9
// CHECK:STDOUT: store ptr %.loc13_17.2, ptr %b.var, align 8, !dbg !10
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(i64 8, ptr %c.var), !dbg !7
// CHECK:STDOUT: store ptr %b.var, ptr %c.var, align 8, !dbg !11
// CHECK:STDOUT: %.loc15_12 = load ptr, ptr %c.var, align 8, !dbg !12
// CHECK:STDOUT: %.loc15_11.2 = load ptr, ptr %.loc15_12, align 8, !dbg !13
// CHECK:STDOUT: %.loc15_10.2 = load i32, ptr %.loc15_11.2, align 4, !dbg !14
// CHECK:STDOUT: ret i32 %.loc15_10.2, !dbg !15
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
// CHECK:STDOUT: declare void @llvm.lifetime.start.p0(i64 immarg, ptr nocapture) #0
// CHECK:STDOUT:
// CHECK:STDOUT: ; uselistorder directives
// CHECK:STDOUT: uselistorder ptr @llvm.lifetime.start.p0, { 2, 1, 0 }
// CHECK:STDOUT:
// CHECK:STDOUT: attributes #0 = { nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
// CHECK:STDOUT:
// CHECK:STDOUT: !llvm.module.flags = !{!0, !1}
// CHECK:STDOUT: !llvm.dbg.cu = !{!2}
// CHECK:STDOUT:
@@ -45,12 +56,10 @@ fn F(p: i32**) -> i32 {
// CHECK:STDOUT: !6 = !{}
// CHECK:STDOUT: !7 = !DILocation(line: 12, column: 7, scope: !4)
// CHECK:STDOUT: !8 = !DILocation(line: 12, column: 3, scope: !4)
// CHECK:STDOUT: !9 = !DILocation(line: 13, column: 7, scope: !4)
// CHECK:STDOUT: !10 = !DILocation(line: 13, column: 17, scope: !4)
// CHECK:STDOUT: !11 = !DILocation(line: 13, column: 3, scope: !4)
// CHECK:STDOUT: !12 = !DILocation(line: 14, column: 7, scope: !4)
// CHECK:STDOUT: !13 = !DILocation(line: 14, column: 3, scope: !4)
// CHECK:STDOUT: !14 = !DILocation(line: 15, column: 12, scope: !4)
// CHECK:STDOUT: !15 = !DILocation(line: 15, column: 11, scope: !4)
// CHECK:STDOUT: !16 = !DILocation(line: 15, column: 10, scope: !4)
// CHECK:STDOUT: !17 = !DILocation(line: 15, column: 3, scope: !4)
// CHECK:STDOUT: !9 = !DILocation(line: 13, column: 17, scope: !4)
// CHECK:STDOUT: !10 = !DILocation(line: 13, column: 3, scope: !4)
// CHECK:STDOUT: !11 = !DILocation(line: 14, column: 3, scope: !4)
// CHECK:STDOUT: !12 = !DILocation(line: 15, column: 12, scope: !4)
// CHECK:STDOUT: !13 = !DILocation(line: 15, column: 11, scope: !4)
// CHECK:STDOUT: !14 = !DILocation(line: 15, column: 10, scope: !4)
// CHECK:STDOUT: !15 = !DILocation(line: 15, column: 3, scope: !4)