[PATCH] D141747: Resolve a FIXME in MachineCopyPropagation by allowig propagation to subregister uses.

[Owen Anderson via Phabricator via llvm-commits]

resistor updated this revision to Diff 489670.
resistor added a comment.

Update for review feedback.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D141747/new/

https://reviews.llvm.org/D141747

Files:
  llvm/lib/CodeGen/MachineCopyPropagation.cpp
  llvm/test/CodeGen/Thumb2/mve-vst3.ll


Index: llvm/test/CodeGen/Thumb2/mve-vst3.ll
===================================================================
--- llvm/test/CodeGen/Thumb2/mve-vst3.ll
+++ llvm/test/CodeGen/Thumb2/mve-vst3.ll
@@ -166,44 +166,43 @@
 ; CHECK-NEXT:    vmov.f32 s22, s3
 ; CHECK-NEXT:    vstrw.32 q7, [sp, #48] @ 16-byte Spill
 ; CHECK-NEXT:    vmov.f32 s9, s0
-; CHECK-NEXT:    vmov.f32 s8, s4
-; CHECK-NEXT:    vmov.f32 s11, s5
 ; CHECK-NEXT:    vmov.f32 s0, s30
-; CHECK-NEXT:    vstrw.32 q2, [sp, #128] @ 16-byte Spill
 ; CHECK-NEXT:    vmov.f32 s1, s15
-; CHECK-NEXT:    vldrw.u32 q2, [sp, #16] @ 16-byte Reload
 ; CHECK-NEXT:    vmov.f32 s2, s19
 ; CHECK-NEXT:    vmov.f32 s3, s31
 ; CHECK-NEXT:    vstrw.32 q0, [sp, #112] @ 16-byte Spill
+; CHECK-NEXT:    vmov.f32 s8, s4
+; CHECK-NEXT:    vmov.f32 s11, s5
 ; CHECK-NEXT:    vmov.f32 s0, s17
+; CHECK-NEXT:    vstrw.32 q2, [sp, #128] @ 16-byte Spill
 ; CHECK-NEXT:    vmov.f32 s2, s14
+; CHECK-NEXT:    vldrw.u32 q2, [sp, #16] @ 16-byte Reload
 ; CHECK-NEXT:    vmov.f32 s3, s18
 ; CHECK-NEXT:    vmov.f32 s21, s7
+; CHECK-NEXT:    vldrw.u32 q1, [sp] @ 16-byte Reload
 ; CHECK-NEXT:    vstrw.32 q0, [sp, #96] @ 16-byte Spill
 ; CHECK-NEXT:    vldrw.u32 q0, [sp, #144] @ 16-byte Reload
 ; CHECK-NEXT:    vstrw.32 q5, [r1, #32]
-; CHECK-NEXT:    vmov.f32 s22, s11
-; CHECK-NEXT:    vldrw.u32 q1, [sp] @ 16-byte Reload
-; CHECK-NEXT:    vmov.f64 d0, d4
-; CHECK-NEXT:    vmov.f32 s19, s10
-; CHECK-NEXT:    vldrw.u32 q2, [sp, #80] @ 16-byte Reload
 ; CHECK-NEXT:    vmov.f32 s21, s7
-; CHECK-NEXT:    vmov.f64 d14, d4
 ; CHECK-NEXT:    vmov.f32 s20, s2
 ; CHECK-NEXT:    vmov.f32 s23, s3
+; CHECK-NEXT:    vldrw.u32 q0, [sp, #64] @ 16-byte Reload
+; CHECK-NEXT:    vmov.f32 s22, s11
 ; CHECK-NEXT:    vstrw.32 q5, [sp, #32] @ 16-byte Spill
 ; CHECK-NEXT:    vmov.f32 s21, s16
 ; CHECK-NEXT:    vmov.f32 s23, s13
-; CHECK-NEXT:    vmov.f32 s16, s1
-; CHECK-NEXT:    vmov.f32 s13, s0
-; CHECK-NEXT:    vldrw.u32 q0, [sp, #64] @ 16-byte Reload
+; CHECK-NEXT:    vmov.f32 s16, s9
+; CHECK-NEXT:    vmov.f32 s19, s10
+; CHECK-NEXT:    vmov.f32 s13, s8
+; CHECK-NEXT:    vldrw.u32 q2, [sp, #80] @ 16-byte Reload
+; CHECK-NEXT:    vmov.f32 s20, s12
+; CHECK-NEXT:    vmov.f64 d14, d4
 ; CHECK-NEXT:    vmov r0, r3, d14
 ; CHECK-NEXT:    vldrw.u32 q7, [sp, #48] @ 16-byte Reload
 ; CHECK-NEXT:    vmov.f32 s7, s11
 ; CHECK-NEXT:    vmov.f32 s8, s24
 ; CHECK-NEXT:    vmov.f32 s9, s0
 ; CHECK-NEXT:    vmov.f32 s11, s25
-; CHECK-NEXT:    vmov.f32 s20, s12
 ; CHECK-NEXT:    vmov.f32 s12, s4
 ; CHECK-NEXT:    vmov.f32 s4, s10
 ; CHECK-NEXT:    vmov.32 q2[2], r0
Index: llvm/lib/CodeGen/MachineCopyPropagation.cpp
===================================================================
--- llvm/lib/CodeGen/MachineCopyPropagation.cpp
+++ llvm/lib/CodeGen/MachineCopyPropagation.cpp
@@ -595,12 +595,15 @@
     const MachineOperand &CopySrc = *CopyOperands->Source;
     Register CopySrcReg = CopySrc.getReg();
 
-    // FIXME: Don't handle partial uses of wider COPYs yet.
+    // When the use is a subregister of the COPY destination,
+    // record the subreg index.
+    unsigned SubregIdx = 0;
+
+    // This can only occur when we are dealing with physical registers.
     if (MOUse.getReg() != CopyDstReg) {
-      LLVM_DEBUG(
-          dbgs() << "MCP: FIXME! Not forwarding COPY to sub-register use:\n  "
-                 << MI);
-      continue;
+      SubregIdx = TRI->getSubRegIndex(CopyDstReg, MOUse.getReg());
+      if (!SubregIdx)
+        continue;
     }
 
     // Don't forward COPYs of reserved regs unless they are constant.
@@ -633,7 +636,11 @@
                       << "\n     with " << printReg(CopySrcReg, TRI)
                       << "\n     in " << MI << "     from " << *Copy);
 
-    MOUse.setReg(CopySrcReg);
+    if (SubregIdx)
+      MOUse.setReg(TRI->getSubReg(CopySrcReg, SubregIdx));
+    else
+      MOUse.setReg(CopySrcReg);
+
     if (!CopySrc.isRenamable())
       MOUse.setIsRenamable(false);
     MOUse.setIsUndef(CopySrc.isUndef());


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