[PATCH] D91512: [AArch64][Isel] Avoid implicit zext for SIGN_EXTEND_INREG ( TRUNCATE )

[guopeilin via Phabricator via llvm-commits]

guopeilin updated this revision to Diff 307938.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D91512/new/

https://reviews.llvm.org/D91512

Files:
  llvm/lib/Target/AArch64/AArch64ISelLowering.h
  llvm/test/CodeGen/AArch64/aarch64-avoid-implicit-zext-for-sign_extend_inreg.ll


Index: llvm/test/CodeGen/AArch64/aarch64-avoid-implicit-zext-for-sign_extend_inreg.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/aarch64-avoid-implicit-zext-for-sign_extend_inreg.ll
@@ -0,0 +1,16 @@
+; RUN: llc -O3 -mtriple=aarch64-unknown-linux-gnu < %s | FileCheck %s
+ at c = common dso_local global i64 0, align 8
+
+define dso_local i32 @main(i64 %bf.load) {
+entry:
+  %0 = lshr i64 %bf.load, 30
+  %sext3 = shl nuw nsw i64 %0, 16
+  %sext = trunc i64 %sext3 to i32
+  %conv.i = ashr exact i32 %sext, 16
+  %conv.i.i = zext i32 %conv.i to i64
+; CHECK:        // %bb.0:
+; CHECK:        sbfx    x{{[0-9]+}}, x{{[0-9]+}}, #{{[0-9]+}}, #{{[0-9]+}}
+; CHECK-NEXT:   mov     w{{[0-9]+}}, w{{[0-9]+}}
+  store i64 %conv.i.i, i64* @c, align 8
+  ret i32 0
+}
Index: llvm/lib/Target/AArch64/AArch64ISelLowering.h
===================================================================
--- llvm/lib/Target/AArch64/AArch64ISelLowering.h
+++ llvm/lib/Target/AArch64/AArch64ISelLowering.h
@@ -432,6 +432,16 @@
 // FIXME: X86 also checks for CMOV here. Do we need something similar?
 static inline bool isDef32(const SDNode &N) {
   unsigned Opc = N.getOpcode();
+
+  // For some cases, isBitfieldExtractOpFromSExtInReg() will try to use
+  // SBFMXri + COPY to implement sign_extend_inreg(truncate) during ISel,
+  // However COPY is likely to be erased after register coalescing, So if
+  // we want to zext this value, we need avoid using implicit way.
+  if (Opc == ISD::SIGN_EXTEND_INREG) {
+    SDValue Opr = N.getOperand(0);
+    return Opr->getOpcode() != ISD::TRUNCATE;
+  }
+
   return Opc != ISD::TRUNCATE && Opc != TargetOpcode::EXTRACT_SUBREG &&
          Opc != ISD::CopyFromReg && Opc != ISD::AssertSext &&
          Opc != ISD::AssertZext;


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