[llvm] [Float2Int] Fix miscompile with floats that can be converted to large values (PR #85996)
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llvm-commits at lists.llvm.org
Wed Mar 20 13:51:38 PDT 2024
https://github.com/AtariDreams updated https://github.com/llvm/llvm-project/pull/85996
>From e858f092c0d00bdfd0d371e8b52f8f1f3c15de72 Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Wed, 20 Mar 2024 13:24:30 -0400
Subject: [PATCH 1/2] [Float2Int] Pre-commit tests NFC)
---
llvm/test/Transforms/Float2Int/basic.ll | 52 +++++++++++++++++++++++++
1 file changed, 52 insertions(+)
diff --git a/llvm/test/Transforms/Float2Int/basic.ll b/llvm/test/Transforms/Float2Int/basic.ll
index 2854a83179b7eb..050227e53fff7a 100644
--- a/llvm/test/Transforms/Float2Int/basic.ll
+++ b/llvm/test/Transforms/Float2Int/basic.ll
@@ -349,3 +349,55 @@ bogusBB: ; preds = %bogusBB
%tobool = fcmp une double %inc, 0.000000e+00
br label %bogusBB
}
+
+define i32 @pr79158() {
+; CHECK-LABEL: @pr79158(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[X_I:%.*]] = alloca i32, align 4
+; CHECK-NEXT: call void @llvm.lifetime.start.p0(i64 4, ptr nonnull [[X_I]])
+; CHECK-NEXT: store volatile i32 1, ptr [[X_I]], align 4
+; CHECK-NEXT: [[X_I_0_X_I_0_X_0_X_0_X_0__I:%.*]] = load volatile i32, ptr [[X_I]], align 4
+; CHECK-NEXT: [[CMP_I:%.*]] = icmp sgt i32 [[X_I_0_X_I_0_X_0_X_0_X_0__I]], 0
+; CHECK-NEXT: [[TMP0:%.*]] = zext i1 [[CMP_I]] to i32
+; CHECK-NEXT: [[MUL_I1:%.*]] = mul i32 [[TMP0]], 2147483647
+; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 4, ptr nonnull [[X_I]])
+; CHECK-NEXT: ret i32 0
+;
+entry:
+ %x.i = alloca i32, align 4
+ call void @llvm.lifetime.start.p0(i64 4, ptr nonnull %x.i)
+ store volatile i32 1, ptr %x.i, align 4
+ %x.i.0.x.i.0.x.0.x.0.x.0..i = load volatile i32, ptr %x.i, align 4
+ %cmp.i = icmp sgt i32 %x.i.0.x.i.0.x.0.x.0.x.0..i, 0
+ %conv.i = uitofp i1 %cmp.i to double
+ %mul.i = fmul double %conv.i, 0x41EFFFFFFFE00000
+ %conv1.i = fptoui double %mul.i to i32
+ call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %x.i)
+ ret i32 0
+}
+
+define i32 @pr79158_2() {
+; CHECK-LABEL: @pr79158_2(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[X_I:%.*]] = alloca i32, align 4
+; CHECK-NEXT: call void @llvm.lifetime.start.p0(i64 4, ptr nonnull [[X_I]])
+; CHECK-NEXT: store volatile i32 1, ptr [[X_I]], align 4
+; CHECK-NEXT: [[X_I_0_X_I_0_X_0_X_0_X_0__I:%.*]] = load volatile i32, ptr [[X_I]], align 4
+; CHECK-NEXT: [[CMP_I:%.*]] = icmp sgt i32 [[X_I_0_X_I_0_X_0_X_0_X_0__I]], 0
+; CHECK-NEXT: [[TMP0:%.*]] = zext i1 [[CMP_I]] to i32
+; CHECK-NEXT: [[MUL_I1:%.*]] = mul i32 [[TMP0]], 2147483647
+; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 4, ptr nonnull [[X_I]])
+; CHECK-NEXT: ret i32 0
+;
+entry:
+ %x.i = alloca i32, align 4
+ call void @llvm.lifetime.start.p0(i64 4, ptr nonnull %x.i)
+ store volatile i32 1, ptr %x.i, align 4
+ %x.i.0.x.i.0.x.0.x.0.x.0..i = load volatile i32, ptr %x.i, align 4
+ %cmp.i = icmp sgt i32 %x.i.0.x.i.0.x.0.x.0.x.0..i, 0
+ %conv.i = uitofp i1 %cmp.i to double
+ %mul.i = fmul double %conv.i, 2147483648.0
+ %conv1.i = fptoui double %mul.i to i32
+ call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %x.i)
+ ret i32 0
+}
>From cdece8c17246f17f5467544e0eb5c7b8a764642c Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Wed, 20 Mar 2024 15:34:39 -0400
Subject: [PATCH 2/2] [Float2Int] Fix miscompile with floats that can be
converted to large values
There is an issue with Float2Int whenever it has to deal with floats that evaluate to numbers that are over INT_MAX, but under UINT_MAX.
Simply, because the conversion method always assumes a signed integer, this works until the 32 bit number is actually a positive 32 bit number that would be interpreted as a negative number when evaluated as an integer, being put in an i32.
This was messing up the Float2Int conversions and causing miscompiles.
To fix this, tell the APSInt constructor if the value is positive or negative.
---
llvm/lib/Transforms/Scalar/Float2Int.cpp | 7 +++----
llvm/test/Transforms/Float2Int/basic.ll | 4 ++--
2 files changed, 5 insertions(+), 6 deletions(-)
diff --git a/llvm/lib/Transforms/Scalar/Float2Int.cpp b/llvm/lib/Transforms/Scalar/Float2Int.cpp
index ccca8bcc1a56ac..2805a9adeaec5e 100644
--- a/llvm/lib/Transforms/Scalar/Float2Int.cpp
+++ b/llvm/lib/Transforms/Scalar/Float2Int.cpp
@@ -409,11 +409,10 @@ Value *Float2IntPass::convert(Instruction *I, Type *ToTy) {
} else if (Instruction *VI = dyn_cast<Instruction>(V)) {
NewOperands.push_back(convert(VI, ToTy));
} else if (ConstantFP *CF = dyn_cast<ConstantFP>(V)) {
- APSInt Val(ToTy->getPrimitiveSizeInBits(), /*isUnsigned=*/false);
+ const APFloat &F = CF->getValueAPF();
+ APSInt Val(ToTy->getPrimitiveSizeInBits(), !F.isNegative());
bool Exact;
- CF->getValueAPF().convertToInteger(Val,
- APFloat::rmNearestTiesToEven,
- &Exact);
+ F.convertToInteger(Val, APFloat::rmNearestTiesToEven, &Exact);
NewOperands.push_back(ConstantInt::get(ToTy, Val));
} else {
llvm_unreachable("Unhandled operand type?");
diff --git a/llvm/test/Transforms/Float2Int/basic.ll b/llvm/test/Transforms/Float2Int/basic.ll
index 050227e53fff7a..90180a8462f0b2 100644
--- a/llvm/test/Transforms/Float2Int/basic.ll
+++ b/llvm/test/Transforms/Float2Int/basic.ll
@@ -359,7 +359,7 @@ define i32 @pr79158() {
; CHECK-NEXT: [[X_I_0_X_I_0_X_0_X_0_X_0__I:%.*]] = load volatile i32, ptr [[X_I]], align 4
; CHECK-NEXT: [[CMP_I:%.*]] = icmp sgt i32 [[X_I_0_X_I_0_X_0_X_0_X_0__I]], 0
; CHECK-NEXT: [[TMP0:%.*]] = zext i1 [[CMP_I]] to i32
-; CHECK-NEXT: [[MUL_I1:%.*]] = mul i32 [[TMP0]], 2147483647
+; CHECK-NEXT: [[MUL_I1:%.*]] = mul i32 [[TMP0]], -1
; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 4, ptr nonnull [[X_I]])
; CHECK-NEXT: ret i32 0
;
@@ -385,7 +385,7 @@ define i32 @pr79158_2() {
; CHECK-NEXT: [[X_I_0_X_I_0_X_0_X_0_X_0__I:%.*]] = load volatile i32, ptr [[X_I]], align 4
; CHECK-NEXT: [[CMP_I:%.*]] = icmp sgt i32 [[X_I_0_X_I_0_X_0_X_0_X_0__I]], 0
; CHECK-NEXT: [[TMP0:%.*]] = zext i1 [[CMP_I]] to i32
-; CHECK-NEXT: [[MUL_I1:%.*]] = mul i32 [[TMP0]], 2147483647
+; CHECK-NEXT: [[MUL_I1:%.*]] = mul i32 [[TMP0]], -2147483648
; CHECK-NEXT: call void @llvm.lifetime.end.p0(i64 4, ptr nonnull [[X_I]])
; CHECK-NEXT: ret i32 0
;
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