Use TLI.isZExtFree and TLI.isTruncateFree

Author: dc03-work

llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp

@@ -3153,10 +3153,22 @@ bool CombinerHelper::matchHoistLogicOpWithSameOpcodeHands(
     return false;
   case TargetOpcode::G_ANYEXT:
   case TargetOpcode::G_SEXT:
-  case TargetOpcode::G_ZEXT:
-  case TargetOpcode::G_TRUNC: {
+  case TargetOpcode::G_ZEXT: {
     // Match: logic (ext X), (ext Y) --> ext (logic X, Y)
+    break;
+  }
+  case TargetOpcode::G_TRUNC: {
     // Match: logic (trunc X), (trunc Y) -> trunc (logic X, Y)
+    MachineFunction *MF = MI.getMF();
+    EVT DstEVT = getApproximateEVTForLLT(MRI.getType(Dst), MF->getDataLayout(),
+                                         MF->getFunction().getContext());
+    EVT XEVT = getApproximateEVTForLLT(XTy, MF->getDataLayout(),
+                                       MF->getFunction().getContext());
+    const TargetLowering &TLI = getTargetLowering();
+    // Be extra careful sinking truncate. If it's free, there's no benefit in
+    // widening a binop.
+    if (TLI.isZExtFree(DstEVT, XEVT) && TLI.isTruncateFree(XEVT, DstEVT))
+      return false;
     break;
   }
   case TargetOpcode::G_AND:

llvm/test/CodeGen/AArch64/GlobalISel/prelegalizer-combiner-narrow-binop-feeding-add.mir

@@ -84,9 +84,10 @@ body:             |
     ; CHECK: liveins: $x0, $x1
     ; CHECK: %binop_lhs:_(s64) = COPY $x0
     ; CHECK: %binop_rhs:_(s64) = COPY $x1
-    ; CHECK: [[AND:%[0-9]+]]:_(s64) = G_AND %binop_lhs, %binop_rhs
-    ; CHECK: [[TRUNC:%[0-9]+]]:_(s32) = G_TRUNC [[AND]](s64)
-    ; CHECK: [[ZEXT:%[0-9]+]]:_(s64) = G_ZEXT [[TRUNC]](s32)
+    ; CHECK: [[TRUNC:%[0-9]+]]:_(s32) = G_TRUNC %binop_lhs(s64)
+    ; CHECK: [[TRUNC1:%[0-9]+]]:_(s32) = G_TRUNC %binop_rhs(s64)
+    ; CHECK: [[AND:%[0-9]+]]:_(s32) = G_AND [[TRUNC]], [[TRUNC1]]
+    ; CHECK: [[ZEXT:%[0-9]+]]:_(s64) = G_ZEXT [[AND]](s32)
     ; CHECK: $x0 = COPY [[ZEXT]](s64)
     ; CHECK: RET_ReallyLR implicit $x0
     %binop_lhs:_(s64) = COPY $x0
@@ -130,9 +131,10 @@ body:             |
     ; CHECK: liveins: $x0, $x1
     ; CHECK: %binop_lhs:_(s64) = COPY $x0
     ; CHECK: %binop_rhs:_(s64) = COPY $x1
-    ; CHECK: [[XOR:%[0-9]+]]:_(s64) = G_XOR %binop_lhs, %binop_rhs
-    ; CHECK: [[TRUNC:%[0-9]+]]:_(s32) = G_TRUNC [[XOR]](s64)
-    ; CHECK: [[ZEXT:%[0-9]+]]:_(s64) = G_ZEXT [[TRUNC]](s32)
+    ; CHECK: [[TRUNC:%[0-9]+]]:_(s32) = G_TRUNC %binop_lhs(s64)
+    ; CHECK: [[TRUNC1:%[0-9]+]]:_(s32) = G_TRUNC %binop_rhs(s64)
+    ; CHECK: [[XOR:%[0-9]+]]:_(s32) = G_XOR [[TRUNC]], [[TRUNC1]]
+    ; CHECK: [[ZEXT:%[0-9]+]]:_(s64) = G_ZEXT [[XOR]](s32)
     ; CHECK: $x0 = COPY [[ZEXT]](s64)
     ; CHECK: RET_ReallyLR implicit $x0
     %binop_lhs:_(s64) = COPY $x0