[RISCV] Miscompile with -O3 #90380
Assignees
Labels
Comments
|
@llvm/issue-subscribers-backend-risc-v Author: Yingwei Zheng (dtcxzyw)
Reduced test case:
```
#include "csmith.h"
uint8_t a = 55;
int32_t b;
int32_t c[4];
uint32_t e[4];
void f() {
int32_t *o = &c[1];
*o = 223;
if (safe_mod_func_uint8_t_u_u(safe_sub_func_uint8_t_u_u(b, 1), a |= *o)) {
e[0] = ++a;
}
}
int main() {
b = 0;
f();
printf("%d\n", a);
return 0;
}
```
```
> bin/clang -O0 --target=riscv64-linux-gnu test.c -I/usr/include/csmith -w
> qemu-riscv64 -L /usr/riscv64-linux-gnu/ a.out
255
> bin/clang -O3 --target=riscv64-linux-gnu test.c -I/usr/include/csmith -w
> qemu-riscv64 -L /usr/riscv64-linux-gnu/ a.out
224
```
llvm version: d6c4ebb
|
dtcxzyw
added a commit
that referenced
this issue
Apr 29, 2024
See the following case: ``` define i8 @SRC1(i8 %x) { entry: %cmp = icmp eq i8 %x, -1 br i1 %cmp, label %exit, label %if.then if.then: %inc = add nuw nsw i8 %x, 1 br label %exit exit: %retval = phi i8 [ %inc, %if.then ], [ -1, %entry ] ret i8 %retval } define i8 @tgt1(i8 %x) { entry: %inc = add nuw nsw i8 %x, 1 %0 = icmp eq i8 %inc, 0 br i1 %0, label %exit, label %if.then if.then: ; preds = %entry br label %exit exit: ; preds = %if.then, %entry %retval = phi i8 [ %inc, %if.then ], [ -1, %entry ] ret i8 %retval } ``` `optimizeBranch` converts `icmp eq X, -1` into cmp to zero on RISC-V and hoists the add into the entry block. Poison-generating flags should be dropped as they don't still hold. Proof: https://alive2.llvm.org/ce/z/sP7mvK Fixes #90380
llvmbot
pushed a commit
to llvmbot/llvm-project
that referenced
this issue
Apr 29, 2024
See the following case: ``` define i8 @SRC1(i8 %x) { entry: %cmp = icmp eq i8 %x, -1 br i1 %cmp, label %exit, label %if.then if.then: %inc = add nuw nsw i8 %x, 1 br label %exit exit: %retval = phi i8 [ %inc, %if.then ], [ -1, %entry ] ret i8 %retval } define i8 @tgt1(i8 %x) { entry: %inc = add nuw nsw i8 %x, 1 %0 = icmp eq i8 %inc, 0 br i1 %0, label %exit, label %if.then if.then: ; preds = %entry br label %exit exit: ; preds = %if.then, %entry %retval = phi i8 [ %inc, %if.then ], [ -1, %entry ] ret i8 %retval } ``` `optimizeBranch` converts `icmp eq X, -1` into cmp to zero on RISC-V and hoists the add into the entry block. Poison-generating flags should be dropped as they don't still hold. Proof: https://alive2.llvm.org/ce/z/sP7mvK Fixes llvm#90380 (cherry picked from commit ab12bba)
tstellar
pushed a commit
to llvmbot/llvm-project
that referenced
this issue
Apr 30, 2024
See the following case: ``` define i8 @SRC1(i8 %x) { entry: %cmp = icmp eq i8 %x, -1 br i1 %cmp, label %exit, label %if.then if.then: %inc = add nuw nsw i8 %x, 1 br label %exit exit: %retval = phi i8 [ %inc, %if.then ], [ -1, %entry ] ret i8 %retval } define i8 @tgt1(i8 %x) { entry: %inc = add nuw nsw i8 %x, 1 %0 = icmp eq i8 %inc, 0 br i1 %0, label %exit, label %if.then if.then: ; preds = %entry br label %exit exit: ; preds = %if.then, %entry %retval = phi i8 [ %inc, %if.then ], [ -1, %entry ] ret i8 %retval } ``` `optimizeBranch` converts `icmp eq X, -1` into cmp to zero on RISC-V and hoists the add into the entry block. Poison-generating flags should be dropped as they don't still hold. Proof: https://alive2.llvm.org/ce/z/sP7mvK Fixes llvm#90380 (cherry picked from commit ab12bba)
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Reduced test case:
llvm version: d6c4ebb
The text was updated successfully, but these errors were encountered: