[llvm] 4225f54 - [InstCombine] Fold abs of known sign operand when source is sub
via llvm-commits
llvm-commits at lists.llvm.org
Sun Aug 6 21:00:04 PDT 2023
Author: Zhongyunde
Date: 2023-08-07T11:55:11+08:00
New Revision: 4225f54bf576daf1555de44f71670bbc7c7e5923
URL: https://github.com/llvm/llvm-project/commit/4225f54bf576daf1555de44f71670bbc7c7e5923
DIFF: https://github.com/llvm/llvm-project/commit/4225f54bf576daf1555de44f71670bbc7c7e5923.diff
LOG: [InstCombine] Fold abs of known sign operand when source is sub
abs(x-y) --> x-y where x >= y, done on D122013
abs(x-y) --> y-x where x <= y
proofs: https://alive2.llvm.org/ce/z/KkeEsd
Reviewed By: goldstein.w.n, nikic
Differential Revision: https://reviews.llvm.org/D156499
Added:
Modified:
llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
llvm/test/Transforms/InstCombine/abs-intrinsic.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index a4960bac1fe827..15cbcf90cfd155 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1018,6 +1018,20 @@ static std::optional<bool> getKnownSign(Value *Op, Instruction *CxtI,
ICmpInst::ICMP_SLT, Op, Constant::getNullValue(Op->getType()), CxtI, DL);
}
+static std::optional<bool> getKnownSignOrZero(Value *Op, Instruction *CxtI,
+ const DataLayout &DL,
+ AssumptionCache *AC,
+ DominatorTree *DT) {
+ if (std::optional<bool> Sign = getKnownSign(Op, CxtI, DL, AC, DT))
+ return Sign;
+
+ Value *X, *Y;
+ if (match(Op, m_NSWSub(m_Value(X), m_Value(Y))))
+ return isImpliedByDomCondition(ICmpInst::ICMP_SLE, X, Y, CxtI, DL);
+
+ return std::nullopt;
+}
+
/// Return true if two values \p Op0 and \p Op1 are known to have the same sign.
static bool signBitMustBeTheSame(Value *Op0, Value *Op1, Instruction *CxtI,
const DataLayout &DL, AssumptionCache *AC,
@@ -1518,12 +1532,15 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
if (match(IIOperand, m_Select(m_Value(), m_Neg(m_Value(X)), m_Deferred(X))))
return replaceOperand(*II, 0, X);
- if (std::optional<bool> Sign = getKnownSign(IIOperand, II, DL, &AC, &DT)) {
- // abs(x) -> x if x >= 0
- if (!*Sign)
+ if (std::optional<bool> Known =
+ getKnownSignOrZero(IIOperand, II, DL, &AC, &DT)) {
+ // abs(x) -> x if x >= 0 (include abs(x-y) --> x - y where x >= y)
+ // abs(x) -> x if x > 0 (include abs(x-y) --> x - y where x > y)
+ if (!*Known)
return replaceInstUsesWith(*II, IIOperand);
// abs(x) -> -x if x < 0
+ // abs(x) -> -x if x < = 0 (include abs(x-y) --> y - x where x <= y)
if (IntMinIsPoison)
return BinaryOperator::CreateNSWNeg(IIOperand);
return BinaryOperator::CreateNeg(IIOperand);
diff --git a/llvm/test/Transforms/InstCombine/abs-intrinsic.ll b/llvm/test/Transforms/InstCombine/abs-intrinsic.ll
index 4e8427b9ee7727..50bdd643528d96 100644
--- a/llvm/test/Transforms/InstCombine/abs-intrinsic.ll
+++ b/llvm/test/Transforms/InstCombine/abs-intrinsic.ll
@@ -486,11 +486,10 @@ define i32 @sub_abs_sgeT_swap(i32 %x, i32 %y) {
; CHECK-NEXT: [[CMP_NOT:%.*]] = icmp slt i32 [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: br i1 [[CMP_NOT]], label [[COND_END:%.*]], label [[COND_TRUE:%.*]]
; CHECK: cond.true:
-; CHECK-NEXT: [[SUB:%.*]] = sub nsw i32 [[X]], [[Y]]
-; CHECK-NEXT: [[TMP0:%.*]] = call i32 @llvm.abs.i32(i32 [[SUB]], i1 true)
+; CHECK-NEXT: [[SUB_NEG:%.*]] = sub i32 [[Y]], [[X]]
; CHECK-NEXT: br label [[COND_END]]
; CHECK: cond.end:
-; CHECK-NEXT: [[R:%.*]] = phi i32 [ [[TMP0]], [[COND_TRUE]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[R:%.*]] = phi i32 [ [[SUB_NEG]], [[COND_TRUE]] ], [ 0, [[ENTRY:%.*]] ]
; CHECK-NEXT: ret i32 [[R]]
;
entry:
@@ -567,11 +566,10 @@ define i32 @sub_abs_sle(i32 %x, i32 %y) {
; CHECK-NEXT: [[CMP_NOT:%.*]] = icmp sgt i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: br i1 [[CMP_NOT]], label [[COND_END:%.*]], label [[COND_TRUE:%.*]]
; CHECK: cond.true:
-; CHECK-NEXT: [[SUB:%.*]] = sub nsw i32 [[X]], [[Y]]
-; CHECK-NEXT: [[TMP0:%.*]] = call i32 @llvm.abs.i32(i32 [[SUB]], i1 true)
+; CHECK-NEXT: [[SUB_NEG:%.*]] = sub i32 [[Y]], [[X]]
; CHECK-NEXT: br label [[COND_END]]
; CHECK: cond.end:
-; CHECK-NEXT: [[R:%.*]] = phi i32 [ [[TMP0]], [[COND_TRUE]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[R:%.*]] = phi i32 [ [[SUB_NEG]], [[COND_TRUE]] ], [ 0, [[ENTRY:%.*]] ]
; CHECK-NEXT: ret i32 [[R]]
;
entry:
@@ -595,11 +593,10 @@ define i8 @sub_abs_sleF(i8 %x, i8 %y) {
; CHECK-NEXT: [[CMP_NOT:%.*]] = icmp sgt i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: br i1 [[CMP_NOT]], label [[COND_END:%.*]], label [[COND_TRUE:%.*]]
; CHECK: cond.true:
-; CHECK-NEXT: [[SUB:%.*]] = sub nsw i8 [[X]], [[Y]]
-; CHECK-NEXT: [[TMP0:%.*]] = call i8 @llvm.abs.i8(i8 [[SUB]], i1 false)
+; CHECK-NEXT: [[SUB_NEG:%.*]] = sub i8 [[Y]], [[X]]
; CHECK-NEXT: br label [[COND_END]]
; CHECK: cond.end:
-; CHECK-NEXT: [[R:%.*]] = phi i8 [ [[TMP0]], [[COND_TRUE]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[R:%.*]] = phi i8 [ [[SUB_NEG]], [[COND_TRUE]] ], [ 0, [[ENTRY:%.*]] ]
; CHECK-NEXT: ret i8 [[R]]
;
entry:
@@ -622,11 +619,10 @@ define i8 @sub_abs_sleT(i8 %x, i8 %y) {
; CHECK-NEXT: [[CMP_NOT:%.*]] = icmp sgt i8 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: br i1 [[CMP_NOT]], label [[COND_END:%.*]], label [[COND_TRUE:%.*]]
; CHECK: cond.true:
-; CHECK-NEXT: [[SUB:%.*]] = sub nsw i8 [[X]], [[Y]]
-; CHECK-NEXT: [[TMP0:%.*]] = call i8 @llvm.abs.i8(i8 [[SUB]], i1 true)
+; CHECK-NEXT: [[SUB_NEG:%.*]] = sub i8 [[Y]], [[X]]
; CHECK-NEXT: br label [[COND_END]]
; CHECK: cond.end:
-; CHECK-NEXT: [[R:%.*]] = phi i8 [ [[TMP0]], [[COND_TRUE]] ], [ 0, [[ENTRY:%.*]] ]
+; CHECK-NEXT: [[R:%.*]] = phi i8 [ [[SUB_NEG]], [[COND_TRUE]] ], [ 0, [[ENTRY:%.*]] ]
; CHECK-NEXT: ret i8 [[R]]
;
entry:
More information about the llvm-commits
mailing list