[ARM][atomicrmw] Fix CMP_SWAP_32 expand assert

This assert is intended to ensure that the high registers are not
selected when it is passed to one of the thumb UXT instructions. However
it was triggering even for 32 bit where no UXT instruction is emitted.

Fixes PR51313.

Differential Revision: https://reviews.llvm.org/D107363

Author: tmatheson-arm

llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp

@@ -1647,7 +1647,7 @@ bool ARMExpandPseudo::ExpandCMP_SWAP(MachineBasicBlock &MBB,
            "CMP_SWAP not expected to be custom expanded for Thumb1");
     assert((UxtOp == 0 || UxtOp == ARM::tUXTB || UxtOp == ARM::tUXTH) &&
            "ARMv8-M.baseline does not have t2UXTB/t2UXTH");
-    assert(ARM::tGPRRegClass.contains(DesiredReg) &&
+    assert((UxtOp == 0 || ARM::tGPRRegClass.contains(DesiredReg)) &&
            "DesiredReg used for UXT op must be tGPR");
   }
 

llvm/test/CodeGen/ARM/cmpxchg.mir

@@ -1,5 +1,6 @@
 # NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
 # RUN: llc -o - %s -mtriple=armv7-unknown-linux-gnu -verify-machineinstrs -run-pass=arm-pseudo | FileCheck %s
+# RUN: llc -o - %s -mtriple=thumbv7-unknown-linux-gnu -verify-machineinstrs -run-pass=arm-pseudo | FileCheck %s --check-prefix=THUMB
 ---
 name: func
 tracksRegLiveness: true
@@ -23,5 +24,62 @@ body: |
     ; CHECK: CMPri killed $r2, 0, 14 /* CC::al */, $noreg, implicit-def $cpsr
     ; CHECK: Bcc %bb.1, 1 /* CC::ne */, killed $cpsr
     ; CHECK: .3:
+    ; THUMB-LABEL: name: func
+    ; THUMB: successors: %bb.1(0x80000000)
+    ; THUMB: liveins: $r0_r1, $r4_r5, $r3, $lr
+    ; THUMB: .1:
+    ; THUMB: successors: %bb.3(0x40000000), %bb.2(0x40000000)
+    ; THUMB: liveins: $r4, $r5, $r3
+    ; THUMB: $r0, $r1 = t2LDREXD $r3, 14 /* CC::al */, $noreg
+    ; THUMB: tCMPhir killed $r0, $r4, 14 /* CC::al */, $noreg, implicit-def $cpsr
+    ; THUMB: tCMPhir killed $r1, $r5, 0 /* CC::eq */, killed $cpsr, implicit-def $cpsr
+    ; THUMB: tBcc %bb.3, 1 /* CC::ne */, killed $cpsr
+    ; THUMB: .2:
+    ; THUMB: successors: %bb.1(0x40000000), %bb.3(0x40000000)
+    ; THUMB: liveins: $r4, $r5, $r3
+    ; THUMB: early-clobber $r2 = t2STREXD $r4, $r5, $r3, 14 /* CC::al */, $noreg
+    ; THUMB: t2CMPri killed $r2, 0, 14 /* CC::al */, $noreg, implicit-def $cpsr
+    ; THUMB: tBcc %bb.1, 1 /* CC::ne */, killed $cpsr
+    ; THUMB: .3:
     dead early-clobber renamable $r0_r1, dead early-clobber renamable $r2 = CMP_SWAP_64 killed renamable $r3, killed renamable $r4_r5, renamable $r4_r5 :: (volatile load store monotonic monotonic (s64))
 ...
+---
+name: func2
+tracksRegLiveness: true
+body: |
+  bb.0:
+    liveins: $r1, $r2, $r3, $r12, $lr
+    ; CHECK-LABEL: name: func2
+    ; CHECK: successors: %bb.1(0x80000000)
+    ; CHECK: liveins: $r1, $r2, $r3, $r12, $lr
+    ; CHECK: .1:
+    ; CHECK: successors: %bb.3(0x40000000), %bb.2(0x40000000)
+    ; CHECK: liveins: $lr, $r3, $r12
+    ; CHECK: $r1 = LDREX $r3, 14 /* CC::al */, $noreg
+    ; CHECK: CMPrr killed $r1, $r12, 14 /* CC::al */, $noreg, implicit-def $cpsr
+    ; CHECK: Bcc %bb.3, 1 /* CC::ne */, killed $cpsr
+    ; CHECK: .2:
+    ; CHECK: successors: %bb.1(0x40000000), %bb.3(0x40000000)
+    ; CHECK: liveins: $lr, $r3, $r12
+    ; CHECK: early-clobber $r2 = STREX $lr, $r3, 14 /* CC::al */, $noreg
+    ; CHECK: CMPri killed $r2, 0, 14 /* CC::al */, $noreg, implicit-def $cpsr
+    ; CHECK: Bcc %bb.1, 1 /* CC::ne */, killed $cpsr
+    ; CHECK: .3:
+    ; THUMB-LABEL: name: func2
+    ; THUMB: successors: %bb.1(0x80000000)
+    ; THUMB: liveins: $r1, $r2, $r3, $r12, $lr
+    ; THUMB: .1:
+    ; THUMB: successors: %bb.3(0x40000000), %bb.2(0x40000000)
+    ; THUMB: liveins: $lr, $r3, $r12
+    ; THUMB: $r1 = t2LDREX $r3, 0, 14 /* CC::al */, $noreg
+    ; THUMB: tCMPhir killed $r1, $r12, 14 /* CC::al */, $noreg, implicit-def $cpsr
+    ; THUMB: tBcc %bb.3, 1 /* CC::ne */, killed $cpsr
+    ; THUMB: .2:
+    ; THUMB: successors: %bb.1(0x40000000), %bb.3(0x40000000)
+    ; THUMB: liveins: $lr, $r3, $r12
+    ; THUMB: early-clobber $r2 = t2STREX $lr, $r3, 0, 14 /* CC::al */, $noreg
+    ; THUMB: t2CMPri killed $r2, 0, 14 /* CC::al */, $noreg, implicit-def $cpsr
+    ; THUMB: tBcc %bb.1, 1 /* CC::ne */, killed $cpsr
+    ; THUMB: .3:
+    dead early-clobber renamable $r1, dead early-clobber renamable $r2 = CMP_SWAP_32 killed renamable $r3, killed renamable $r12, killed renamable $lr
+...