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[InstCombine] Adjust usub_sat fold one use checks

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This adjusts the one use checks in the the usub_sat fold code to not
increase instruction count, but otherwise do the fold. Reviewed as a
part of D69514.
This commit is contained in:
David Green
2019-11-30 16:58:00 +00:00
parent a46b959ebd
commit 3a1bef5616
2 changed files with 12 additions and 13 deletions
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llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+3 -3
View File
@@ -711,9 +711,9 @@ static Value *canonicalizeSaturatedSubtract(const ICmpInst *ICI,
else if (!match(TrueVal, m_Sub(m_Specific(A), m_Specific(B))))
return nullptr;
// If sub is used anywhere else, we wouldn't be able to eliminate it
// afterwards.
if (!TrueVal->hasOneUse())
// If we are adding a negate and the sub and icmp are used anywhere else, we
// would end up with more instructions.
if (IsNegative && !TrueVal->hasOneUse() && !ICI->hasOneUse())
return nullptr;
// (a > b) ? a - b : 0 -> usub.sat(a, b)
llvm/test/Transforms/InstCombine/unsigned_saturated_sub.ll
+9 -10
View File
@@ -36,11 +36,10 @@ define i64 @max_sub_uge(i64 %a, i64 %b) {
define i64 @max_sub_uge_extrause1(i64 %a, i64 %b) {
; CHECK-LABEL: @max_sub_uge_extrause1(
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i64 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: [[SUB:%.*]] = sub i64 [[A]], [[B]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i64 0, i64 [[SUB]]
; CHECK-NEXT: [[SUB:%.*]] = sub i64 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[A]], i64 [[B]])
; CHECK-NEXT: call void @use(i64 [[SUB]])
; CHECK-NEXT: ret i64 [[SEL]]
; CHECK-NEXT: ret i64 [[TMP1]]
;
%cmp = icmp uge i64 %a, %b
%sub = sub i64 %a, %b
@@ -67,10 +66,10 @@ define i64 @max_sub_uge_extrause3(i64 %a, i64 %b) {
; CHECK-LABEL: @max_sub_uge_extrause3(
; CHECK-NEXT: [[CMP:%.*]] = icmp uge i64 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: [[SUB:%.*]] = sub i64 [[A]], [[B]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i64 [[SUB]], i64 0
; CHECK-NEXT: [[TMP1:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[A]], i64 [[B]])
; CHECK-NEXT: call void @use(i64 [[SUB]])
; CHECK-NEXT: call void @usei1(i1 [[CMP]])
; CHECK-NEXT: ret i64 [[SEL]]
; CHECK-NEXT: ret i64 [[TMP1]]
;
%cmp = icmp uge i64 %a, %b
%sub = sub i64 %a, %b
@@ -205,11 +204,11 @@ define i64 @neg_max_sub_ugt_sel_swapped_extrause1(i64 %a, i64 %b) {
define i64 @neg_max_sub_ugt_sel_swapped_extrause2(i64 %a, i64 %b) {
; CHECK-LABEL: @neg_max_sub_ugt_sel_swapped_extrause2(
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i64 [[B:%.*]], [[A:%.*]]
; CHECK-NEXT: [[SUB:%.*]] = sub i64 [[B]], [[A]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i64 0, i64 [[SUB]]
; CHECK-NEXT: [[SUB:%.*]] = sub i64 [[B:%.*]], [[A:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = call i64 @llvm.usub.sat.i64(i64 [[A]], i64 [[B]])
; CHECK-NEXT: [[TMP2:%.*]] = sub i64 0, [[TMP1]]
; CHECK-NEXT: call void @use(i64 [[SUB]])
; CHECK-NEXT: ret i64 [[SEL]]
; CHECK-NEXT: ret i64 [[TMP2]]
;
%cmp = icmp ugt i64 %b, %a
%sub = sub i64 %b, %a