[PATCH] D59256: [ARM] Disable LDM with offset for thumb2 cortex-m cpus

[Dave Green via Phabricator via llvm-commits]

dmgreen updated this revision to Diff 190282.
dmgreen marked an inline comment as done.
dmgreen added a comment.

Now minsize


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D59256/new/

https://reviews.llvm.org/D59256

Files:
  llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
  llvm/test/CodeGen/Thumb2/ldstopt-addm.ll


Index: llvm/test/CodeGen/Thumb2/ldstopt-addm.ll
===================================================================
--- llvm/test/CodeGen/Thumb2/ldstopt-addm.ll
+++ llvm/test/CodeGen/Thumb2/ldstopt-addm.ll
@@ -22,8 +22,9 @@
 ;
 ; CHECK-LABEL: test:
 ; CHECK:       @ %bb.0: @ %entry
-; CHECK-NEXT:    add.w r3, r0, #48
-; CHECK-NEXT:    ldm r3, {r1, r2, r3}
+; CHECK-NEXT:    ldr r1, [r0, #48]
+; CHECK-NEXT:    ldr r2, [r0, #52]
+; CHECK-NEXT:    ldr r3, [r0, #56]
 ; CHECK-NEXT:    ldr r0, [r0, #60]
 ; CHECK-NEXT:    add r0, r3
 ; CHECK-NEXT:    add r1, r2
Index: llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
===================================================================
--- llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
+++ llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
@@ -673,6 +673,10 @@
     if (!SafeToClobberCPSR)
       return nullptr;
 
+    // On M class cores, the extra add will only increase latency
+    if (STI->isMClass() && !isThumb1 && !MF->getFunction().optForMinSize())
+      return nullptr;
+
     unsigned NewBase;
     if (isi32Load(Opcode)) {
       // If it is a load, then just use one of the destination registers


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