[PATCH] D21151: AMDGPU: Preserve undef flag on vcc when shrinking v_cndmask_b32

[Matt Arsenault via llvm-commits]

arsenm updated this revision to Diff 60104.
arsenm added a comment.

Go back to preserving kill


http://reviews.llvm.org/D21151

Files:
  lib/Target/AMDGPU/SIShrinkInstructions.cpp
  test/CodeGen/AMDGPU/cndmask-no-def-vcc.ll

Index: test/CodeGen/AMDGPU/cndmask-no-def-vcc.ll
===================================================================
--- test/CodeGen/AMDGPU/cndmask-no-def-vcc.ll
+++ test/CodeGen/AMDGPU/cndmask-no-def-vcc.ll
@@ -25,29 +25,3 @@
 bb2:
   ret void
 }
-
-; The undef flag on the condition src must be preserved on the
-; implicit vcc use to avoid verifier errors.
-
-; GCN-LABEL: {{^}}preserve_condition_undef_flag:
-; GCN-NOT: vcc
-; GCN: v_cndmask_b32_e32 v{{[0-9]+}}, 1.0, v{{[0-9]+}}, vcc
-; GCN: v_cndmask_b32_e64 v1, 0, 1, s{{\[[0-9]+:[0-9]+\]}}
-define void @preserve_condition_undef_flag(float %arg, i32 %arg1, float %arg2) {
-bb0:
-  %tmp = icmp sgt i32 %arg1, 4
-  %tmp4 = select i1 undef, float %arg, float 1.000000e+00
-  %tmp5 = fcmp ogt float %arg2, 0.000000e+00
-  %tmp6 = fcmp olt float %arg2, 1.000000e+00
-  %tmp7 = fcmp olt float %arg, %tmp4
-  %tmp8 = and i1 %tmp5, %tmp6
-  %tmp9 = and i1 %tmp8, %tmp7
-  br i1 %tmp9, label %bb1, label %bb2
-
-bb1:
-  store volatile i32 0, i32 addrspace(1)* undef
-  br label %bb2
-
-bb2:
-  ret void
-}
Index: lib/Target/AMDGPU/SIShrinkInstructions.cpp
===================================================================
--- lib/Target/AMDGPU/SIShrinkInstructions.cpp
+++ lib/Target/AMDGPU/SIShrinkInstructions.cpp
@@ -184,16 +184,18 @@
 }
 
 // Copy MachineOperand with all flags except setting it as implicit.
-static void copyFlagsToImplicitVCC(MachineInstr &MI,
-                                   const MachineOperand &Orig) {
-
-  for (MachineOperand &Use : MI.implicit_operands()) {
-    if (Use.getReg() == AMDGPU::VCC) {
-      Use.setIsUndef(Orig.isUndef());
-      Use.setIsKill(Orig.isKill());
-      return;
-    }
-  }
+static MachineOperand copyRegOperandAsImplicit(const MachineOperand &Orig) {
+  assert(!Orig.isImplicit());
+  return MachineOperand::CreateReg(Orig.getReg(),
+                                   Orig.isDef(),
+                                   true,
+                                   Orig.isKill(),
+                                   Orig.isDead(),
+                                   Orig.isUndef(),
+                                   Orig.isEarlyClobber(),
+                                   Orig.getSubReg(),
+                                   Orig.isDebug(),
+                                   Orig.isInternalRead());
 }
 
 static bool isKImmOperand(const SIInstrInfo *TII, const MachineOperand &Src) {
@@ -396,9 +398,10 @@
           Inst32.addOperand(*Src2);
         } else {
           // In the case of V_CNDMASK_B32_e32, the explicit operand src2 is
-          // replaced with an implicit read of vcc. This was already added
-          // during the initial BuildMI, so find it to preserve the flags.
-          copyFlagsToImplicitVCC(*Inst32, *Src2);
+          // replaced with an implicit read of vcc.
+          assert(Src2->getReg() == AMDGPU::VCC &&
+                 "Unexpected missing register operand");
+          Inst32.addOperand(copyRegOperandAsImplicit(*Src2));
         }
       }
 


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