[llvm] Signed integer overflow in Constraint Elimination pass (PR #133903)
via llvm-commits
llvm-commits at lists.llvm.org
Wed Apr 2 05:33:37 PDT 2025
https://github.com/houngkoungting updated https://github.com/llvm/llvm-project/pull/133903
>From ff8cdb3c75b5d01ff99d229d3322434a35e9333f 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: Mon, 31 Mar 2025 09:12:33 +0800
Subject: [PATCH 1/6] Update MathExtras.h
---
llvm/include/llvm/Support/MathExtras.h | 48 ++++++++++++++++----------
1 file changed, 30 insertions(+), 18 deletions(-)
diff --git a/llvm/include/llvm/Support/MathExtras.h b/llvm/include/llvm/Support/MathExtras.h
index 519fcc8fde5d5..513885d5473f2 100644
--- a/llvm/include/llvm/Support/MathExtras.h
+++ b/llvm/include/llvm/Support/MathExtras.h
@@ -760,31 +760,43 @@ 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
- // 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;
+ // Handle zero case
+ if (X == 0 || Y == 0) {
+ Result = 0;
+ return false;
+ }
- // Convert to signed.
- const bool IsNegative = (X < 0) ^ (Y < 0);
- Result = IsNegative ? (0 - UResult) : UResult;
+ bool IsNegative = (X < 0) ^ (Y < 0);
- // If any of the args was 0, result is 0 and no overflow occurs.
- if (UX == 0 || UY == 0)
- return false;
+ // Safely compute absolute values
+ 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);
- // 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;
+ // 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 bf508ac437bc06e369027db4c046004866b22e69 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: Mon, 31 Mar 2025 09:23:44 +0800
Subject: [PATCH 2/6] Update MathExtras.h
---
llvm/include/llvm/Support/MathExtras.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/llvm/include/llvm/Support/MathExtras.h b/llvm/include/llvm/Support/MathExtras.h
index 513885d5473f2..00fd097ff8674 100644
--- a/llvm/include/llvm/Support/MathExtras.h
+++ b/llvm/include/llvm/Support/MathExtras.h
@@ -771,7 +771,7 @@ std::enable_if_t<std::is_signed_v<T>, bool>MulOverflow(T X, T Y, T &Result) {
return false;
}
- bool IsNegative = (X < 0) ^ (Y < 0);
+ const bool IsNegative = (X < 0) ^ (Y < 0);
// Safely compute absolute values
const U AbsX = X < 0 ? (0 - static_cast<U>(X)) : static_cast<U>(X);
>From 50f7f5579be672c05e4991949b3600904384b934 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, 1 Apr 2025 20:06:38 +0800
Subject: [PATCH 3/6] Update MathExtras.h
---
llvm/include/llvm/Support/MathExtras.h | 24 +++++++++++-------------
1 file changed, 11 insertions(+), 13 deletions(-)
diff --git a/llvm/include/llvm/Support/MathExtras.h b/llvm/include/llvm/Support/MathExtras.h
index 00fd097ff8674..caac64e69afa2 100644
--- a/llvm/include/llvm/Support/MathExtras.h
+++ b/llvm/include/llvm/Support/MathExtras.h
@@ -113,7 +113,7 @@ static const unsigned char BitReverseTable256[256] = {
#define R2(n) n, n + 2 * 64, n + 1 * 64, n + 3 * 64
#define R4(n) R2(n), R2(n + 2 * 16), R2(n + 1 * 16), R2(n + 3 * 16)
#define R6(n) R4(n), R4(n + 2 * 4), R4(n + 1 * 4), R4(n + 3 * 4)
- R6(0), R6(2), R6(1), R6(3)
+ R6(0), R6(2), R6(1), R6(3)
#undef R2
#undef R4
#undef R6
@@ -183,8 +183,7 @@ template <unsigned N> constexpr bool isInt(int64_t x) {
}
/// Checks if a signed integer is an N bit number shifted left by S.
-template <unsigned N, unsigned S>
-constexpr bool isShiftedInt(int64_t x) {
+template <unsigned N, unsigned S> constexpr bool isShiftedInt(int64_t x) {
static_assert(S < 64, "isShiftedInt<N, S> with S >= 64 is too much.");
static_assert(N + S <= 64, "isShiftedInt<N, S> with N + S > 64 is too wide.");
return isInt<N + S>(x) && (x % (UINT64_C(1) << S) == 0);
@@ -207,8 +206,7 @@ template <unsigned N> constexpr bool isUInt(uint64_t x) {
}
/// Checks if a unsigned integer is an N bit number shifted left by S.
-template <unsigned N, unsigned S>
-constexpr bool isShiftedUInt(uint64_t x) {
+template <unsigned N, unsigned S> constexpr bool isShiftedUInt(uint64_t x) {
static_assert(S < 64, "isShiftedUInt<N, S> with S >= 64 is too much.");
static_assert(N + S <= 64,
"isShiftedUInt<N, S> with N + S > 64 is too wide.");
@@ -757,23 +755,22 @@ std::enable_if_t<std::is_signed_v<T>, T> SubOverflow(T X, T Y, T &Result) {
#endif
}
-/// 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>, bool>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
using U = std::make_unsigned_t<T>;
+
// Handle zero case
if (X == 0 || Y == 0) {
Result = 0;
return false;
}
- const bool IsNegative = (X < 0) ^ (Y < 0);
+ bool IsNegative = (X < 0) ^ (Y < 0);
- // Safely compute absolute values
+ // Safely compute absolute values (convert to int64_t first)
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);
@@ -783,12 +780,13 @@ std::enable_if_t<std::is_signed_v<T>, bool>MulOverflow(T X, T Y, T &Result) {
// Safe to multiply
U AbsResult = AbsX * AbsY;
- Result = IsNegative ? static_cast<T>(0-AbsResult) : static_cast<T>(AbsResult);
-
+ 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
+ return true; // overflow
}
U Limit = IsNegative ? MaxNegative : MaxPositive;
>From 7f9fc784bdcf7f1756e70e582a6c7a437eb9a3c6 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, 1 Apr 2025 20:09:43 +0800
Subject: [PATCH 4/6] Update MathExtras.h
>From bd0f01c71b564c3da11ee1c533ac8739a14de104 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, 1 Apr 2025 20:17:58 +0800
Subject: [PATCH 5/6] Update MathExtras.h
---
llvm/include/llvm/Support/MathExtras.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/llvm/include/llvm/Support/MathExtras.h b/llvm/include/llvm/Support/MathExtras.h
index caac64e69afa2..526dad5021753 100644
--- a/llvm/include/llvm/Support/MathExtras.h
+++ b/llvm/include/llvm/Support/MathExtras.h
@@ -770,7 +770,7 @@ std::enable_if_t<std::is_signed_v<T>, bool> MulOverflow(T X, T Y, T &Result) {
bool IsNegative = (X < 0) ^ (Y < 0);
- // Safely compute absolute values (convert to int64_t first)
+ // Safely compute absolute values
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);
>From 0eeb32246e3743fc1edd6fd3c14d38c9a1ef651e 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, 1 Apr 2025 20:18:50 +0800
Subject: [PATCH 6/6] Update MathExtras.h
---
llvm/include/llvm/Support/MathExtras.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/llvm/include/llvm/Support/MathExtras.h b/llvm/include/llvm/Support/MathExtras.h
index 526dad5021753..ccb954646bb50 100644
--- a/llvm/include/llvm/Support/MathExtras.h
+++ b/llvm/include/llvm/Support/MathExtras.h
@@ -770,7 +770,7 @@ std::enable_if_t<std::is_signed_v<T>, bool> MulOverflow(T X, T Y, T &Result) {
bool IsNegative = (X < 0) ^ (Y < 0);
- // Safely compute absolute values
+ // Safely compute absolute values
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);
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