Thanks again to Jeff Law and Andrew Pinski. Here's a revised patch that
addresses the true underlying cause of PR 128333. recog.cc's cancel_changes
was not correctly updating the recog_data cache, which leads to strange
(incorrect) behavior in fwprop and ifcvt.
This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
and make -k check, both with and without --target_board=unix{-m32},
with no new failures. Ok for mainline?
2026-02-05 Roger Sayle <[email protected]>
Andrew Pinski <[email protected]>
Jeff Law <[email protected]>
gcc/ChangeLog
PR rtl-optimization/123833
* recog.cc (cancel_changes): Update the recog_data cache if it
holds the instruction being changed.
gcc/testsuite
PR rtl-optimization/123833
* gcc.target/mips/pr123833.c: New test case.
diff --git a/gcc/recog.cc b/gcc/recog.cc
index a0b4925a8ee..04864065424 100644
--- a/gcc/recog.cc
+++ b/gcc/recog.cc
@@ -608,7 +608,11 @@ cancel_changes (int num)
else
*changes[i].loc = changes[i].old;
if (changes[i].object && !MEM_P (changes[i].object))
- INSN_CODE (changes[i].object) = changes[i].old_code;
+ {
+ INSN_CODE (changes[i].object) = changes[i].old_code;
+ if (recog_data.insn == changes[i].object)
+ recog_data.insn = nullptr;
+ }
}
num_changes = num;
}
diff --git a/gcc/testsuite/gcc.target/mips/pr123833.c
b/gcc/testsuite/gcc.target/mips/pr123833.c
new file mode 100644
index 00000000000..4d0c9e8eaec
--- /dev/null
+++ b/gcc/testsuite/gcc.target/mips/pr123833.c
@@ -0,0 +1,26 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -mabi=64 -mhard-float" } */
+
+typedef short int16_t;
+typedef signed char int8_t;
+typedef long long int64_t;
+typedef unsigned char uint8_t;
+typedef unsigned long long uint64_t;
+
+#define BS_VEC(type, num) type __attribute__((vector_size(num * sizeof(type))))
+BS_VEC(int8_t, 2) backsmith_pure_0(int64_t);
+uint64_t backsmith_pure_4(int16_t BS_ARG_0)
+{
+ BS_VEC(int16_t, 16)
+ BS_VAR_0 = __builtin_convertvector(
+ __builtin_shufflevector(backsmith_pure_0(0), backsmith_pure_0(0), 0, 2,
+ 2, 3, 2, 1, 2, 3, 0, 2, 0, 0, 2, 2, 0, 1),
+ BS_VEC(int16_t, 16));
+ for (;;)
+ {
+ if (__builtin_ctzg((uint8_t)BS_VAR_0[3], BS_ARG_0))
+ for (;;);
+ return 0;
+ }
+}
+
