[llvm] [Float2Int] Fix miscompile with floats that can be converted to large values (PR #85996)
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Wed Mar 20 17:26:54 PDT 2024
https://github.com/AtariDreams updated https://github.com/llvm/llvm-project/pull/85996
>From 6c52be200f23f6f89d5c8b0625ec02a5e4d3006c 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..f3d749b60e162c 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 [[MUL_I1]]
+;
+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, 4294967295.0
+ %conv1.i = fptoui double %mul.i to i32
+ call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %x.i)
+ ret i32 %conv1.i
+}
+
+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 [[MUL_I1]]
+;
+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 %conv1.i
+}
>From 0f5fca47e182d1c260b440634991e0750673dc70 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 f3d749b60e162c..4c118a4e55f432 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 [[MUL_I1]]
;
@@ -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 [[MUL_I1]]
;
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