[CVP] Stop CVP constant propagation from destroying llvm.assume#183688
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[CVP] Stop CVP constant propagation from destroying llvm.assume#183688
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@llvm/pr-subscribers-llvm-transforms Author: None (lijinpei-amd) ChangesFor following code sequence: CVP may replace all use of Full diff: https://github.com/llvm/llvm-project/pull/183688.diff 3 Files Affected:
diff --git a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
index f4897034569c6..37e46e1b52593 100644
--- a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
+++ b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -334,8 +334,14 @@ static bool constantFoldCmp(CmpInst *Cmp, LazyValueInfo *LVI) {
return false;
++NumCmps;
- Cmp->replaceAllUsesWith(Res);
- Cmp->eraseFromParent();
+ Cmp->replaceUsesWithIf(Res, [](Use &use) {
+ if (auto *intrin = dyn_cast<IntrinsicInst>(use.getUser())) {
+ return !intrin->isAssumeLikeIntrinsic();
+ }
+ return true;
+ });
+ if (Cmp->use_empty())
+ Cmp->eraseFromParent();
return true;
}
diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/conflict.ll b/llvm/test/Transforms/CorrelatedValuePropagation/conflict.ll
index 7bba0565d9988..88f4aa12e90f2 100644
--- a/llvm/test/Transforms/CorrelatedValuePropagation/conflict.ll
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/conflict.ll
@@ -58,7 +58,8 @@ define i8 @test3(i8 %a) {
; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i8 [[A:%.*]], 5
; CHECK-NEXT: br i1 [[CMP1]], label [[DEAD:%.*]], label [[EXIT:%.*]]
; CHECK: dead:
-; CHECK-NEXT: call void @llvm.assume(i1 false)
+; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i8 [[A]], 3
+; CHECK-NEXT: call void @llvm.assume(i1 [[CMP2]])
; CHECK-NEXT: ret i8 5
; CHECK: exit:
; CHECK-NEXT: ret i8 0
diff --git a/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll b/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
index 7fb1e0718795d..3c7c17a84bf6b 100644
--- a/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
+++ b/llvm/test/Transforms/CorrelatedValuePropagation/icmp.ll
@@ -6,6 +6,7 @@ target triple = "x86_64-apple-macosx10.10.0"
declare void @check1(i1) #1
declare void @check2(i1) #1
+declare void @check3(i64)
declare void @llvm.assume(i1)
; Make sure we propagate the value of %tmp35 to the true/false cases
@@ -1657,3 +1658,19 @@ if.true:
if.false:
ret void
}
+
+
+define void @test_assume_not_removed(i64 %idx) {
+; CHECK-LABEL: @test_assume_not_removed(
+; CHECK-NEXT: [[IDX1:%.*]] = add nuw i64 [[IDX:%.*]], 1
+; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i64 [[IDX1]], 1
+; CHECK-NEXT: tail call void @llvm.assume(i1 [[CMP]])
+; CHECK-NEXT: tail call void @check3(i64 [[IDX1]])
+; CHECK-NEXT: ret void
+;
+ %idx1 = add i64 %idx, 1
+ %cmp = icmp ugt i64 %idx1, 1
+ tail call void @llvm.assume(i1 %cmp)
+ tail call void @check3(i64 %idx1)
+ ret void
+}
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Does it fix #90206? |
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A consequence of this change is that we'll also stop removing redundant assumes in CVP, that is cases where dominating conditions already imply the assume. But probably that makes sense, as the assume is not trivially redundant. In particular, it may still be of value for ValueTracking based optimizations, which do not have a global view.
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For following code sequence: ``` %cmp = icmp ugt i64 %idx, 1 tail call void @llvm.assume(i1 %cmp) ``` CVP may replace all use of `%cmp` with `true`, and the information about `%idx` is lost. This commit stop CVP from doing that, so that later pass can exploit the `llvm.assume`.
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…vm#183688) For following code sequence: ``` %cmp = icmp ugt i64 %idx, 1 tail call void @llvm.assume(i1 %cmp) ``` CVP may replace all use of `%cmp` with `true`, and the information about `%idx` is lost. This commit stop CVP from doing that, so that later pass can exploit the `llvm.assume`. Fixes llvm#90206.
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…vm#183688) For following code sequence: ``` %cmp = icmp ugt i64 %idx, 1 tail call void @llvm.assume(i1 %cmp) ``` CVP may replace all use of `%cmp` with `true`, and the information about `%idx` is lost. This commit stop CVP from doing that, so that later pass can exploit the `llvm.assume`. Fixes llvm#90206.
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For following code sequence:
CVP may replace all use of
%cmpwithtrue, and the information about%idxis lost. This commit stop CVP from doing that, so that later pass can exploit thellvm.assume.