[llvm] Signed integer overflow in Constraint Elimination pass issue #133154 (PR #133620)
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Sat Mar 29 22:45:57 PDT 2025
https://github.com/houngkoungting created https://github.com/llvm/llvm-project/pull/133620
Adjusted the limit check to use MaxNegative
>From 69c1f2776efc5b6b413712dc396fa1eb0650f3a9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=BB=83=E5=9C=8B=E5=BA=AD?=
<37643576+houngkoungting at users.noreply.github.com>
Date: Sat, 15 Mar 2025 23:14:33 +0800
Subject: [PATCH 1/6] Update InstCombineShifts.cpp
---
llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
index 90cd279e8a457..8404629810918 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
@@ -994,6 +994,11 @@ static bool setShiftFlags(BinaryOperator &I, const SimplifyQuery &Q) {
I.setIsExact();
return true;
}
+ // shr X, cttz(X)
+ if (match(I.getOperand(1), m_Intrinsic<Intrinsic::cttz>(m_Specific(I.getOperand(0))))) {
+ I.setIsExact();
+ return true;
+ }
}
// Compute what we know about shift count.
>From a5e73a03430cf2218aa23a3e89150fb6d474a4be Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=BB=83=E5=9C=8B=E5=BA=AD?=
<37643576+houngkoungting at users.noreply.github.com>
Date: Sat, 15 Mar 2025 23:33:20 +0800
Subject: [PATCH 2/6] Update InstCombineShifts.cpp
---
llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
index 8404629810918..e73bd002b8dc0 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
@@ -994,11 +994,7 @@ static bool setShiftFlags(BinaryOperator &I, const SimplifyQuery &Q) {
I.setIsExact();
return true;
}
- // shr X, cttz(X)
- if (match(I.getOperand(1), m_Intrinsic<Intrinsic::cttz>(m_Specific(I.getOperand(0))))) {
- I.setIsExact();
- return true;
- }
+
}
// Compute what we know about shift count.
>From 2d5181371c2b645b856b9a15c01cbfa86af46b1c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=BB=83=E5=9C=8B=E5=BA=AD?=
<37643576+houngkoungting at users.noreply.github.com>
Date: Tue, 25 Mar 2025 20:57:55 +0800
Subject: [PATCH 3/6] Update InstCombineShifts.cpp
---
llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp | 1 -
1 file changed, 1 deletion(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
index e73bd002b8dc0..90cd279e8a457 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
@@ -994,7 +994,6 @@ static bool setShiftFlags(BinaryOperator &I, const SimplifyQuery &Q) {
I.setIsExact();
return true;
}
-
}
// Compute what we know about shift count.
>From 9a0d4adee2504b3ddced4f38c0ee4a358e49ef36 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=BB=83=E5=9C=8B=E5=BA=AD?=
<37643576+houngkoungting at users.noreply.github.com>
Date: Sun, 30 Mar 2025 12:10:55 +0800
Subject: [PATCH 4/6] Update MathExtras.h
---
llvm/include/llvm/Support/MathExtras.h | 47 ++++++++++++++++----------
1 file changed, 30 insertions(+), 17 deletions(-)
diff --git a/llvm/include/llvm/Support/MathExtras.h b/llvm/include/llvm/Support/MathExtras.h
index 519fcc8fde5d5..d66fe4884bc28 100644
--- a/llvm/include/llvm/Support/MathExtras.h
+++ b/llvm/include/llvm/Support/MathExtras.h
@@ -764,27 +764,40 @@ std::enable_if_t<std::is_signed_v<T>, T> MulOverflow(T X, T Y, T &Result) {
#if __has_builtin(__builtin_mul_overflow)
return __builtin_mul_overflow(X, Y, &Result);
#else
- // Perform the unsigned multiplication on absolute values.
using U = std::make_unsigned_t<T>;
- const U UX = X < 0 ? (0 - static_cast<U>(X)) : static_cast<U>(X);
- const U UY = Y < 0 ? (0 - static_cast<U>(Y)) : static_cast<U>(Y);
- const U UResult = UX * UY;
- // Convert to signed.
- const bool IsNegative = (X < 0) ^ (Y < 0);
- Result = IsNegative ? (0 - UResult) : UResult;
-
- // If any of the args was 0, result is 0 and no overflow occurs.
- if (UX == 0 || UY == 0)
+ // Handle zero case
+ if (X == 0 || Y == 0) {
+ Result = 0;
return false;
+ }
- // UX and UY are in [1, 2^n], where n is the number of digits.
- // Check how the max allowed absolute value (2^n for negative, 2^(n-1) for
- // positive) divided by an argument compares to the other.
- if (IsNegative)
- return UX > (static_cast<U>(std::numeric_limits<T>::max()) + U(1)) / UY;
- else
- return UX > (static_cast<U>(std::numeric_limits<T>::max())) / UY;
+ bool IsNegative = (X < 0) ^ (Y < 0);
+
+ // Safely compute absolute values
+ const U AbsX = X < 0 ? (0 - static_cast<U>(X+1))+1 : static_cast<U>(X);
+ const U AbsY = Y < 0 ? (0 - static_cast<U>(Y+1))+1 : static_cast<U>(Y);
+
+ // Overflow check before actual multiplication
+ constexpr U MaxPositive = static_cast<U>(std::numeric_limits<T>::max());
+ constexpr U MaxNegative = static_cast<U>(std::numeric_limits<T>::max()) + 1;
+
+ // Safe to multiply
+ U AbsResult = AbsX * AbsY;
+ Result = IsNegative ? static_cast<T>(0-AbsResult) : static_cast<T>(AbsResult);
+
+ // Handle INT_MIN * -1 overflow case explicitly
+ if ((X == std::numeric_limits<T>::min() && Y == -1) ||
+ (Y == std::numeric_limits<T>::min() && X == -1)) {
+ return true; // overflow
+ }
+
+ U Limit = IsNegative ? MaxNegative : MaxPositive;
+
+ if (AbsX > Limit / AbsY)
+ return true;
+
+ return false;
#endif
}
>From 5307a5705b83f540d43666c180fdc31fe9dca0e9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=BB=83=E5=9C=8B=E5=BA=AD?=
<37643576+houngkoungting at users.noreply.github.com>
Date: Sun, 30 Mar 2025 13:39:06 +0800
Subject: [PATCH 5/6] Update MathExtras.h
---
llvm/include/llvm/Support/MathExtras.h | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/llvm/include/llvm/Support/MathExtras.h b/llvm/include/llvm/Support/MathExtras.h
index d66fe4884bc28..d0ed2521ef9bf 100644
--- a/llvm/include/llvm/Support/MathExtras.h
+++ b/llvm/include/llvm/Support/MathExtras.h
@@ -760,7 +760,7 @@ std::enable_if_t<std::is_signed_v<T>, T> SubOverflow(T X, T Y, T &Result) {
/// Multiply two signed integers, computing the two's complement truncated
/// result, returning true if an overflow occurred.
template <typename T>
-std::enable_if_t<std::is_signed_v<T>, T> MulOverflow(T X, T Y, T &Result) {
+std::enable_if_t<std::is_signed_v<T>, bool> MulOverflow(T X, T Y, T &Result) {
#if __has_builtin(__builtin_mul_overflow)
return __builtin_mul_overflow(X, Y, &Result);
#else
@@ -775,23 +775,26 @@ std::enable_if_t<std::is_signed_v<T>, T> MulOverflow(T X, T Y, T &Result) {
bool IsNegative = (X < 0) ^ (Y < 0);
// Safely compute absolute values
- const U AbsX = X < 0 ? (0 - static_cast<U>(X+1))+1 : static_cast<U>(X);
- const U AbsY = Y < 0 ? (0 - static_cast<U>(Y+1))+1 : static_cast<U>(Y);
+ const U AbsX = X < 0 ? (0 - static_cast<U>(X)) : static_cast<U>(X);
+ const U AbsY = Y < 0 ? (0 - static_cast<U>(Y)) : static_cast<U>(Y);
// Overflow check before actual multiplication
constexpr U MaxPositive = static_cast<U>(std::numeric_limits<T>::max());
constexpr U MaxNegative = static_cast<U>(std::numeric_limits<T>::max()) + 1;
-
+
// Safe to multiply
U AbsResult = AbsX * AbsY;
Result = IsNegative ? static_cast<T>(0-AbsResult) : static_cast<T>(AbsResult);
+
+
// Handle INT_MIN * -1 overflow case explicitly
if ((X == std::numeric_limits<T>::min() && Y == -1) ||
(Y == std::numeric_limits<T>::min() && X == -1)) {
return true; // overflow
}
+
U Limit = IsNegative ? MaxNegative : MaxPositive;
if (AbsX > Limit / AbsY)
>From e9732627ec5f1cac01c356287914aa90764afe44 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=BB=83=E5=9C=8B=E5=BA=AD?=
<37643576+houngkoungting at users.noreply.github.com>
Date: Sun, 30 Mar 2025 13:42:36 +0800
Subject: [PATCH 6/6] Update MathExtras.h
---
llvm/include/llvm/Support/MathExtras.h | 3 ---
1 file changed, 3 deletions(-)
diff --git a/llvm/include/llvm/Support/MathExtras.h b/llvm/include/llvm/Support/MathExtras.h
index d0ed2521ef9bf..fe6db8fe14019 100644
--- a/llvm/include/llvm/Support/MathExtras.h
+++ b/llvm/include/llvm/Support/MathExtras.h
@@ -786,15 +786,12 @@ std::enable_if_t<std::is_signed_v<T>, bool> MulOverflow(T X, T Y, T &Result) {
U AbsResult = AbsX * AbsY;
Result = IsNegative ? static_cast<T>(0-AbsResult) : static_cast<T>(AbsResult);
-
-
// Handle INT_MIN * -1 overflow case explicitly
if ((X == std::numeric_limits<T>::min() && Y == -1) ||
(Y == std::numeric_limits<T>::min() && X == -1)) {
return true; // overflow
}
-
U Limit = IsNegative ? MaxNegative : MaxPositive;
if (AbsX > Limit / AbsY)
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