[llvm] 2adcec7 - [InstCombine] Simplify with.overflow intrinsics with assumption information (#84016)
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Sun Jan 5 05:15:21 PST 2025
Author: Yingwei Zheng
Date: 2025-01-05T21:15:17+08:00
New Revision: 2adcec7780f3d3027f76c80dbd73085fdee144d7
URL: https://github.com/llvm/llvm-project/commit/2adcec7780f3d3027f76c80dbd73085fdee144d7
DIFF: https://github.com/llvm/llvm-project/commit/2adcec7780f3d3027f76c80dbd73085fdee144d7.diff
LOG: [InstCombine] Simplify with.overflow intrinsics with assumption information (#84016)
This patch recognizes never-overflow assumptions generated by rustc to
improve the codegen.
Please refer to https://github.com/rust-lang/hashbrown/issues/509 for
more details.
Closes https://github.com/rust-lang/hashbrown/issues/509
Closes https://github.com/llvm/llvm-project/issues/80637
Added:
Modified:
llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
llvm/test/Transforms/InstCombine/overflow.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index fd38738e3be80b..cdb2c11ef046ad 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -839,6 +839,35 @@ InstCombinerImpl::foldIntrinsicWithOverflowCommon(IntrinsicInst *II) {
if (OptimizeOverflowCheck(WO->getBinaryOp(), WO->isSigned(), WO->getLHS(),
WO->getRHS(), *WO, OperationResult, OverflowResult))
return createOverflowTuple(WO, OperationResult, OverflowResult);
+
+ // See whether we can optimize the overflow check with assumption information.
+ for (User *U : WO->users()) {
+ if (!match(U, m_ExtractValue<1>(m_Value())))
+ continue;
+
+ for (auto &AssumeVH : AC.assumptionsFor(U)) {
+ if (!AssumeVH)
+ continue;
+ CallInst *I = cast<CallInst>(AssumeVH);
+ if (!match(I->getArgOperand(0), m_Not(m_Specific(U))))
+ continue;
+ if (!isValidAssumeForContext(I, II, /*DT=*/nullptr,
+ /*AllowEphemerals=*/true))
+ continue;
+ Value *Result =
+ Builder.CreateBinOp(WO->getBinaryOp(), WO->getLHS(), WO->getRHS());
+ Result->takeName(WO);
+ if (auto *Inst = dyn_cast<Instruction>(Result)) {
+ if (WO->isSigned())
+ Inst->setHasNoSignedWrap();
+ else
+ Inst->setHasNoUnsignedWrap();
+ }
+ return createOverflowTuple(WO, Result,
+ ConstantInt::getFalse(U->getType()));
+ }
+ }
+
return nullptr;
}
diff --git a/llvm/test/Transforms/InstCombine/overflow.ll b/llvm/test/Transforms/InstCombine/overflow.ll
index a8969a5ed02c36..22e1631f78ee91 100644
--- a/llvm/test/Transforms/InstCombine/overflow.ll
+++ b/llvm/test/Transforms/InstCombine/overflow.ll
@@ -11,7 +11,7 @@ define i32 @test1(i32 %a, i32 %b) nounwind ssp {
; CHECK-NEXT: [[TMP0:%.*]] = extractvalue { i32, i1 } [[SADD]], 1
; CHECK-NEXT: br i1 [[TMP0]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
; CHECK: if.then:
-; CHECK-NEXT: tail call void @throwAnExceptionOrWhatever() #[[ATTR2:[0-9]+]]
+; CHECK-NEXT: tail call void @throwAnExceptionOrWhatever() #[[ATTR3:[0-9]+]]
; CHECK-NEXT: br label [[IF_END]]
; CHECK: if.end:
; CHECK-NEXT: [[SADD_RESULT:%.*]] = extractvalue { i32, i1 } [[SADD]], 0
@@ -49,7 +49,7 @@ define i32 @test2(i32 %a, i32 %b, ptr %P) nounwind ssp {
; CHECK-NEXT: [[TMP0:%.*]] = icmp ugt i64 [[ADD_OFF]], 4294967295
; CHECK-NEXT: br i1 [[TMP0]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
; CHECK: if.then:
-; CHECK-NEXT: tail call void @throwAnExceptionOrWhatever() #[[ATTR2]]
+; CHECK-NEXT: tail call void @throwAnExceptionOrWhatever() #[[ATTR3]]
; CHECK-NEXT: br label [[IF_END]]
; CHECK: if.end:
; CHECK-NEXT: [[CONV9:%.*]] = trunc i64 [[ADD]] to i32
@@ -86,7 +86,7 @@ define i64 @test3(i32 %a, i32 %b) nounwind ssp {
; CHECK-NEXT: [[TMP1:%.*]] = icmp ult i64 [[TMP0]], -4294967296
; CHECK-NEXT: br i1 [[TMP1]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
; CHECK: if.then:
-; CHECK-NEXT: tail call void @throwAnExceptionOrWhatever() #[[ATTR2]]
+; CHECK-NEXT: tail call void @throwAnExceptionOrWhatever() #[[ATTR3]]
; CHECK-NEXT: br label [[IF_END]]
; CHECK: if.end:
; CHECK-NEXT: ret i64 [[ADD]]
@@ -116,7 +116,7 @@ define zeroext i8 @test4(i8 signext %a, i8 signext %b) nounwind ssp {
; CHECK-NEXT: [[CMP:%.*]] = extractvalue { i8, i1 } [[SADD]], 1
; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
; CHECK: if.then:
-; CHECK-NEXT: tail call void @throwAnExceptionOrWhatever() #[[ATTR2]]
+; CHECK-NEXT: tail call void @throwAnExceptionOrWhatever() #[[ATTR3]]
; CHECK-NEXT: unreachable
; CHECK: if.end:
; CHECK-NEXT: [[SADD_RESULT:%.*]] = extractvalue { i8, i1 } [[SADD]], 0
@@ -150,7 +150,7 @@ define i32 @test8(i64 %a, i64 %b) nounwind ssp {
; CHECK-NEXT: [[TMP1:%.*]] = icmp ult i64 [[TMP0]], -4294967296
; CHECK-NEXT: br i1 [[TMP1]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
; CHECK: if.then:
-; CHECK-NEXT: tail call void @throwAnExceptionOrWhatever() #[[ATTR2]]
+; CHECK-NEXT: tail call void @throwAnExceptionOrWhatever() #[[ATTR3]]
; CHECK-NEXT: br label [[IF_END]]
; CHECK: if.end:
; CHECK-NEXT: [[CONV9:%.*]] = trunc i64 [[ADD]] to i32
@@ -171,3 +171,91 @@ if.end:
ret i32 %conv9
}
+define i32 @uadd_no_overflow(i32 %a, i32 %b) {
+; CHECK-LABEL: @uadd_no_overflow(
+; CHECK-NEXT: [[TMP1:%.*]] = add nuw i32 [[A:%.*]], [[B:%.*]]
+; CHECK-NEXT: ret i32 [[TMP1]]
+;
+ %val = tail call { i32, i1 } @llvm.uadd.with.overflow.i32(i32 %a, i32 %b)
+ %ov = extractvalue { i32, i1 } %val, 1
+ %nowrap = xor i1 %ov, true
+ tail call void @llvm.assume(i1 %nowrap)
+ %res = extractvalue { i32, i1 } %val, 0
+ ret i32 %res
+}
+
+define i32 @smul_no_overflow(i32 %a, i32 %b) {
+; CHECK-LABEL: @smul_no_overflow(
+; CHECK-NEXT: [[TMP1:%.*]] = mul nsw i32 [[A:%.*]], [[B:%.*]]
+; CHECK-NEXT: ret i32 [[TMP1]]
+;
+ %val = tail call { i32, i1 } @llvm.smul.with.overflow.i32(i32 %a, i32 %b)
+ %ov = extractvalue { i32, i1 } %val, 1
+ %nowrap = xor i1 %ov, true
+ tail call void @llvm.assume(i1 %nowrap)
+ %res = extractvalue { i32, i1 } %val, 0
+ ret i32 %res
+}
+
+define i32 @smul_overflow(i32 %a, i32 %b) {
+; CHECK-LABEL: @smul_overflow(
+; CHECK-NEXT: [[VAL:%.*]] = tail call { i32, i1 } @llvm.smul.with.overflow.i32(i32 [[A:%.*]], i32 [[B:%.*]])
+; CHECK-NEXT: [[OV:%.*]] = extractvalue { i32, i1 } [[VAL]], 1
+; CHECK-NEXT: tail call void @llvm.assume(i1 [[OV]])
+; CHECK-NEXT: [[RES:%.*]] = extractvalue { i32, i1 } [[VAL]], 0
+; CHECK-NEXT: ret i32 [[RES]]
+;
+ %val = tail call { i32, i1 } @llvm.smul.with.overflow.i32(i32 %a, i32 %b)
+ %ov = extractvalue { i32, i1 } %val, 1
+ tail call void @llvm.assume(i1 %ov)
+ %res = extractvalue { i32, i1 } %val, 0
+ ret i32 %res
+}
+
+define i32 @uadd_no_overflow_invalid1(i32 %a, i32 %b, i1 %cond) {
+; CHECK-LABEL: @uadd_no_overflow_invalid1(
+; CHECK-NEXT: [[VAL:%.*]] = tail call { i32, i1 } @llvm.uadd.with.overflow.i32(i32 [[A:%.*]], i32 [[B:%.*]])
+; CHECK-NEXT: [[RES:%.*]] = extractvalue { i32, i1 } [[VAL]], 0
+; CHECK-NEXT: call void @use(i32 [[RES]])
+; CHECK-NEXT: br i1 [[COND:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: [[OV:%.*]] = extractvalue { i32, i1 } [[VAL]], 1
+; CHECK-NEXT: [[NOWRAP:%.*]] = xor i1 [[OV]], true
+; CHECK-NEXT: tail call void @llvm.assume(i1 [[NOWRAP]])
+; CHECK-NEXT: ret i32 [[RES]]
+; CHECK: if.else:
+; CHECK-NEXT: ret i32 0
+;
+ %val = tail call { i32, i1 } @llvm.uadd.with.overflow.i32(i32 %a, i32 %b)
+ %res = extractvalue { i32, i1 } %val, 0
+ call void @use(i32 %res)
+ br i1 %cond, label %if.then, label %if.else
+if.then:
+ %ov = extractvalue { i32, i1 } %val, 1
+ %nowrap = xor i1 %ov, true
+ tail call void @llvm.assume(i1 %nowrap)
+ ret i32 %res
+if.else:
+ ret i32 0
+}
+
+define i32 @uadd_no_overflow_invalid2(i32 %a, i32 %b, i1 %cond) {
+; CHECK-LABEL: @uadd_no_overflow_invalid2(
+; CHECK-NEXT: [[VAL:%.*]] = tail call { i32, i1 } @llvm.uadd.with.overflow.i32(i32 [[A:%.*]], i32 [[B:%.*]])
+; CHECK-NEXT: [[OV:%.*]] = extractvalue { i32, i1 } [[VAL]], 1
+; CHECK-NEXT: [[NOWRAP:%.*]] = xor i1 [[OV]], true
+; CHECK-NEXT: call void @use(i32 0)
+; CHECK-NEXT: tail call void @llvm.assume(i1 [[NOWRAP]])
+; CHECK-NEXT: [[RES:%.*]] = extractvalue { i32, i1 } [[VAL]], 0
+; CHECK-NEXT: ret i32 [[RES]]
+;
+ %val = tail call { i32, i1 } @llvm.uadd.with.overflow.i32(i32 %a, i32 %b)
+ %ov = extractvalue { i32, i1 } %val, 1
+ %nowrap = xor i1 %ov, true
+ call void @use(i32 0) ; It is not guaranteed to transfer execution to its successors
+ tail call void @llvm.assume(i1 %nowrap)
+ %res = extractvalue { i32, i1 } %val, 0
+ ret i32 %res
+}
+
+declare void @use(i32)
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