From: Richard Earnshaw <rearnsha@arm.com>
Date: Tue, 14 Apr 2026 13:45:38 +0000 (+0100)
Subject: arm: apply stronger checks on conditional-compare patterns [PR123102]
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=HEAD;p=thirdparty%2Fgcc.git

arm: apply stronger checks on conditional-compare patterns [PR123102]

If a conditional compare operation is generated during expand, then
combine may try to substitute into it in order to generate better code;
but if it does so, we need to validate that the optimized sequence is
still a valid conditional compare.  We were skipping those checks and
that can lead to wrong code being generated.

gcc/ChangeLog:
	PR target/123102
	* config/arm/arm.md (*cmp_ite0): Apply stricter checks on the
	comparison mode.
	(*cmp_ite1, *cmp_and, *cmp_ior): Likewise.
---

diff --git a/gcc/config/arm/arm.md b/gcc/config/arm/arm.md
index d9ce482838b..2a72dde3647 100644
--- a/gcc/config/arm/arm.md
+++ b/gcc/config/arm/arm.md
@@ -10133,6 +10133,7 @@
    (set_attr "type" "multiple")]
 )
 
+;; (pred4 && pred5) != 0
 (define_insn "*cmp_ite0"
   [(set (match_operand 6 "dominant_cc_register" "")
 	(compare
@@ -10149,7 +10150,11 @@
 	        "lPy,rI,L,lPy,lPy,rI,rI,L,L")])
 	  (const_int 0))
 	 (const_int 0)))]
-  "TARGET_32BIT"
+  "TARGET_32BIT
+   && GET_MODE (operands[6]) != CCmode
+   && (GET_MODE (operands[6])
+       == arm_select_dominance_cc_mode (operands[4], operands[5],
+					DOM_CC_X_AND_Y))"
   "*
   {
     static const char * const cmp1[NUM_OF_COND_CMP][2] =
@@ -10216,6 +10221,7 @@
            (const_int 10))])]
 )
 
+;; (!pred4 || pred5) != 0
 (define_insn "*cmp_ite1"
   [(set (match_operand 6 "dominant_cc_register" "")
 	(compare
@@ -10232,7 +10238,11 @@
 	        "lPy,rI,L,lPy,lPy,rI,rI,L,L")])
 	  (const_int 1))
 	 (const_int 0)))]
-  "TARGET_32BIT"
+  "TARGET_32BIT
+   && GET_MODE (operands[6]) != CCmode
+   && (GET_MODE (operands[6])
+       == arm_select_dominance_cc_mode (operands[4], operands[5],
+					DOM_CC_NX_OR_Y))"
   "*
   {
     static const char * const cmp1[NUM_OF_COND_CMP][2] =
@@ -10315,7 +10325,11 @@
 	    (match_operand:SI 3 "arm_add_operand"
 	        "lPy,rI,L,lPy,lPy,r,rI,rI,L,L")]))
 	 (const_int 0)))]
-  "TARGET_32BIT"
+  "TARGET_32BIT
+   && GET_MODE (operands[6]) != CCmode
+   && (GET_MODE (operands[6])
+       == arm_select_dominance_cc_mode (operands[4], operands[5],
+					DOM_CC_X_AND_Y))"
   "*
   {
     static const char *const cmp1[NUM_OF_COND_CMP][2] =
@@ -10400,7 +10414,11 @@
 	    (match_operand:SI 3 "arm_add_operand"
 	        "lPy,rI,L,lPy,lPy,r,rI,rI,L,L")]))
 	 (const_int 0)))]
-  "TARGET_32BIT"
+  "TARGET_32BIT
+   && GET_MODE (operands[6]) != CCmode
+   && (GET_MODE (operands[6])
+       == arm_select_dominance_cc_mode (operands[4], operands[5],
+					DOM_CC_X_OR_Y))"
   "*
   {
     static const char *const cmp1[NUM_OF_COND_CMP][2] =