use lookthrucopylike

Author: broxigarchen

llvm/lib/Target/AMDGPU/SIFoldOperands.cpp

@@ -1899,10 +1899,13 @@ bool SIFoldOperandsImpl::tryFoldClamp(MachineInstr &MI) {
   if (!ClampSrc || !MRI->hasOneNonDBGUser(ClampSrc->getReg()))
     return false;
 
+  if (!ClampSrc->getReg().isVirtual())
+    return false;
+
   // Look through COPY. COPY only observed with True16.
-  MachineOperand *DefSrc = lookUpCopyChain(*TII, *MRI, ClampSrc->getReg());
-  MachineInstr *Def = MRI->getVRegDef(
-      DefSrc && DefSrc->isReg() ? DefSrc->getReg() : ClampSrc->getReg());
+  Register DefSrcReg = TRI->lookThruCopyLike(ClampSrc->getReg(), MRI);
+  MachineInstr *Def =
+      MRI->getVRegDef(DefSrcReg.isVirtual() ? DefSrcReg : ClampSrc->getReg());
 
   // The type of clamp must be compatible.
   if (TII->getClampMask(*Def) != TII->getClampMask(MI))

llvm/test/CodeGen/AMDGPU/true16-fold.mir

@@ -165,9 +165,10 @@ body:             |
     ; CHECK-NEXT: [[COPY2:%[0-9]+]]:vgpr_32 = COPY $vgpr0
     ; CHECK-NEXT: [[DEF:%[0-9]+]]:sreg_32 = IMPLICIT_DEF
     ; CHECK-NEXT: [[COPY3:%[0-9]+]]:vgpr_32 = COPY [[DEF]]
-    ; CHECK-NEXT: [[V_FMA_MIXLO_F16_:%[0-9]+]]:vgpr_32 = nofpexcept V_FMA_MIXLO_F16 8, [[COPY2]], 8, [[COPY1]], 0, [[COPY]], 1, [[COPY3]], 0, 0, implicit $mode, implicit $exec
+    ; CHECK-NEXT: [[V_FMA_MIXLO_F16_:%[0-9]+]]:vgpr_32 = nofpexcept V_FMA_MIXLO_F16 8, [[COPY2]], 8, [[COPY1]], 0, [[COPY]], 0, [[COPY3]], 0, 0, implicit $mode, implicit $exec
     ; CHECK-NEXT: $vgpr10_lo16 = COPY [[V_FMA_MIXLO_F16_]]
-    ; CHECK-NEXT: $vgpr0 = COPY [[V_FMA_MIXLO_F16_]]
+    ; CHECK-NEXT: [[V_MAX_F16_t16_e64_:%[0-9]+]]:vgpr_16 = nofpexcept V_MAX_F16_t16_e64 0, $vgpr10_lo16, 0, $vgpr10_lo16, -1, 0, 0, implicit $mode, implicit $exec
+    ; CHECK-NEXT: $vgpr0 = COPY [[V_MAX_F16_t16_e64_]]
     ; CHECK-NEXT: S_ENDPGM 0, implicit $vgpr0
     %0:vgpr_32 = COPY $vgpr2
     %1:vgpr_32 = COPY $vgpr1