[llvm] [ValueTracking] Fix assertion failure when `computeKnownFPClass` returns fcNone (PR #92355)
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Wed May 15 23:51:32 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-analysis
Author: Yingwei Zheng (dtcxzyw)
<details>
<summary>Changes</summary>
Fixes https://github.com/llvm/llvm-project/pull/92084#issuecomment-2114083188.
---
Full diff: https://github.com/llvm/llvm-project/pull/92355.diff
2 Files Affected:
- (modified) llvm/lib/Analysis/ValueTracking.cpp (+2-1)
- (modified) llvm/test/Transforms/InstCombine/known-bits.ll (+40)
``````````diff
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index c8c527a2d4d2f..087cfcc792ee4 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1126,7 +1126,8 @@ static void computeKnownBitsFromOperator(const Operator *I,
KnownFPClass Result = computeKnownFPClass(V, fcAllFlags, Depth + 1, Q);
FPClassTest FPClasses = Result.KnownFPClasses;
- if (Result.isKnownNever(fcNormal | fcSubnormal | fcNan)) {
+ if (FPClasses != fcNone &&
+ Result.isKnownNever(fcNormal | fcSubnormal | fcNan)) {
Known.Zero.setAllBits();
Known.One.setAllBits();
diff --git a/llvm/test/Transforms/InstCombine/known-bits.ll b/llvm/test/Transforms/InstCombine/known-bits.ll
index 7a38020500517..cb404c0b7f889 100644
--- a/llvm/test/Transforms/InstCombine/known-bits.ll
+++ b/llvm/test/Transforms/InstCombine/known-bits.ll
@@ -1658,5 +1658,45 @@ define i32 @test_qnan_only(float nofpclass(snan sub norm zero inf) %x) {
ret i32 %and
}
+; Make sure that we don't crash when the use of x is unreachable.
+define i64 @pr92084(double %x) {
+; CHECK-LABEL: @pr92084(
+; CHECK-NEXT: [[CMP:%.*]] = fcmp uno double [[X:%.*]], 0.000000e+00
+; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN1:%.*]], label [[IF_ELSE:%.*]]
+; CHECK: if.then1:
+; CHECK-NEXT: br i1 [[CMP]], label [[IF_ELSE]], label [[IF_THEN2:%.*]]
+; CHECK: if.then2:
+; CHECK-NEXT: [[CAST:%.*]] = bitcast double [[X]] to i64
+; CHECK-NEXT: [[AND:%.*]] = and i64 [[CAST]], 1
+; CHECK-NEXT: ret i64 [[AND]]
+; CHECK: if.else:
+; CHECK-NEXT: ret i64 0
+;
+ %cmp = fcmp uno double %x, 0.000000e+00
+ br i1 %cmp, label %if.then1, label %if.else
+
+if.then1:
+ br i1 %cmp, label %if.else, label %if.then2
+
+if.then2:
+ %cast = bitcast double %x to i64
+ %and = and i64 %cast, 1
+ ret i64 %and
+
+if.else:
+ ret i64 0
+}
+
+define i32 @test_none(float nofpclass(all) %x) {
+; CHECK-LABEL: @test_none(
+; CHECK-NEXT: [[Y:%.*]] = bitcast float [[X:%.*]] to i32
+; CHECK-NEXT: [[AND:%.*]] = and i32 [[Y]], 4194304
+; CHECK-NEXT: ret i32 [[AND]]
+;
+ %y = bitcast float %x to i32
+ %and = and i32 %y, 4194304
+ ret i32 %and
+}
+
declare void @use(i1)
declare void @sink(i8)
``````````
</details>
https://github.com/llvm/llvm-project/pull/92355
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