[llvm] [PowerPC] Require PPC32 for 32-bit addc/adde/subc/sube (PR #179186)

[Nikita Popov via llvm-commits]

https://github.com/nikic created https://github.com/llvm/llvm-project/pull/179186

Unlike the base add/sub opcodes which will just overflow, these will produce incorrect results, because the carry operates on the full 64-bits. Trying to use these with i32 operands on PPC64 should result in a selection failure instead of a silent miscompile, like the one seen in https://github.com/llvm/llvm-project/pull/178979.

>From 823315d927f7141b8e3349f8fd1a579899a3777e Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov at redhat.com>
Date: Mon, 2 Feb 2026 10:08:19 +0100
Subject: [PATCH] [PowerPC] Require PPC32 for 32-bit addc/adde/subc/sube

---
 llvm/lib/Target/PowerPC/PPCInstrInfo.td | 27 ++++++++++++++++---------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/llvm/lib/Target/PowerPC/PPCInstrInfo.td b/llvm/lib/Target/PowerPC/PPCInstrInfo.td
index 88dd4df7e4366..6b04cd377e00a 100644
--- a/llvm/lib/Target/PowerPC/PPCInstrInfo.td
+++ b/llvm/lib/Target/PowerPC/PPCInstrInfo.td
@@ -2556,7 +2556,7 @@ let Defs = [CARRY] in
 def ADDIC  : DForm_2<12, (outs gprc:$RST), (ins gprc:$RA, s16imm:$D),
                      "addic $RST, $RA, $D", IIC_IntGeneral,
                      [(set i32:$RST, (PPCaddc i32:$RA, imm32SExt16:$D))]>,
-                     RecFormRel, PPC970_DGroup_Cracked;
+                     RecFormRel, PPC970_DGroup_Cracked, Requires<[IsPPC32]>;
 let Defs = [CARRY, CR0] in
 def ADDIC_rec : DForm_2<13, (outs gprc:$RST), (ins gprc:$RA, s16imm:$D),
                      "addic. $RST, $RA, $D", IIC_IntGeneral,
@@ -2576,7 +2576,8 @@ def MULLI  : DForm_2< 7, (outs gprc:$RST), (ins gprc:$RA, s16imm:$D),
 let Defs = [CARRY] in
 def SUBFIC : DForm_2< 8, (outs gprc:$RST), (ins gprc:$RA, s16imm:$D),
                      "subfic $RST, $RA, $D", IIC_IntGeneral,
-                     [(set i32:$RST, (PPCsubc imm32SExt16:$D, i32:$RA))]>;
+                     [(set i32:$RST, (PPCsubc imm32SExt16:$D, i32:$RA))]>,
+                     Requires<[IsPPC32]>;
 
 let isReMaterializable = 1, isAsCheapAsAMove = 1, isMoveImm = 1 in {
   def LI  : DForm_2_r0<14, (outs gprc:$RST), (ins s16imm:$D),
@@ -3175,7 +3176,7 @@ let isCommutable = 1 in
 defm ADDC  : XOForm_1rc<31, 10, 0, (outs gprc:$RT), (ins gprc:$RA, gprc:$RB),
                         "addc", "$RT, $RA, $RB", IIC_IntGeneral,
                         [(set i32:$RT, (PPCaddc i32:$RA, i32:$RB))]>,
-                        PPC970_DGroup_Cracked;
+                        PPC970_DGroup_Cracked, Requires<[IsPPC32]>;
 
 defm DIVW  : XOForm_1rcr<31, 491, 0, (outs gprc:$RT), (ins gprc:$RA, gprc:$RB),
                           "divw", "$RT, $RA, $RB", IIC_IntDivW,
@@ -3208,7 +3209,7 @@ defm SUBF  : XOForm_1rx<31, 40, (outs gprc:$RT), (ins gprc:$RA, gprc:$RB),
 defm SUBFC : XOForm_1rc<31, 8, 0, (outs gprc:$RT), (ins gprc:$RA, gprc:$RB),
                         "subfc", "$RT, $RA, $RB", IIC_IntGeneral,
                         [(set i32:$RT, (PPCsubc i32:$RB, i32:$RA))]>,
-                        PPC970_DGroup_Cracked;
+                        PPC970_DGroup_Cracked, Requires<[IsPPC32]>;
 defm NEG    : XOForm_3r<31, 104, 0, (outs gprc:$RT), (ins gprc:$RA),
                         "neg", "$RT, $RA", IIC_IntSimple,
                         [(set i32:$RT, (ineg i32:$RA))]>;
@@ -3216,22 +3217,28 @@ let Uses = [CARRY] in {
 let isCommutable = 1 in
 defm ADDE  : XOForm_1rc<31, 138, 0, (outs gprc:$RT), (ins gprc:$RA, gprc:$RB),
                         "adde", "$RT, $RA, $RB", IIC_IntGeneral,
-                        [(set i32:$RT, (PPCadde i32:$RA, i32:$RB, CARRY))]>;
+                        [(set i32:$RT, (PPCadde i32:$RA, i32:$RB, CARRY))]>,
+                        Requires<[IsPPC32]>;
 defm ADDME  : XOForm_3rc<31, 234, 0, (outs gprc:$RT), (ins gprc:$RA),
                          "addme", "$RT, $RA", IIC_IntGeneral,
-                         [(set i32:$RT, (PPCadde i32:$RA, -1, CARRY))]>;
+                         [(set i32:$RT, (PPCadde i32:$RA, -1, CARRY))]>,
+                         Requires<[IsPPC32]>;
 defm ADDZE  : XOForm_3rc<31, 202, 0, (outs gprc:$RT), (ins gprc:$RA),
                          "addze", "$RT, $RA", IIC_IntGeneral,
-                         [(set i32:$RT, (PPCadde i32:$RA, 0, CARRY))]>;
+                         [(set i32:$RT, (PPCadde i32:$RA, 0, CARRY))]>,
+                         Requires<[IsPPC32]>;
 defm SUBFE : XOForm_1rc<31, 136, 0, (outs gprc:$RT), (ins gprc:$RA, gprc:$RB),
                         "subfe", "$RT, $RA, $RB", IIC_IntGeneral,
-                        [(set i32:$RT, (PPCsube i32:$RB, i32:$RA, CARRY))]>;
+                        [(set i32:$RT, (PPCsube i32:$RB, i32:$RA, CARRY))]>,
+                        Requires<[IsPPC32]>;
 defm SUBFME : XOForm_3rc<31, 232, 0, (outs gprc:$RT), (ins gprc:$RA),
                          "subfme", "$RT, $RA", IIC_IntGeneral,
-                         [(set i32:$RT, (PPCsube -1, i32:$RA, CARRY))]>;
+                         [(set i32:$RT, (PPCsube -1, i32:$RA, CARRY))]>,
+                         Requires<[IsPPC32]>;
 defm SUBFZE : XOForm_3rc<31, 200, 0, (outs gprc:$RT), (ins gprc:$RA),
                          "subfze", "$RT, $RA", IIC_IntGeneral,
-                         [(set i32:$RT, (PPCsube 0, i32:$RA, CARRY))]>;
+                         [(set i32:$RT, (PPCsube 0, i32:$RA, CARRY))]>,
+                         Requires<[IsPPC32]>;
 }
 }