[PATCH] D91023: [RISCV] Make SIGN_EXTEND_INREG from i8/i16 legal when Zbb extension is enabled.

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: asb, lenary, luismarques, frasercrmck, lewis-revill, PaoloS.
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This produces better code for sign extend to i64 on RV32 target.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D91023

Files:
  llvm/lib/Target/RISCV/RISCVISelLowering.cpp
  llvm/lib/Target/RISCV/RISCVInstrInfoB.td
  llvm/test/CodeGen/RISCV/rv32Zbb.ll


Index: llvm/test/CodeGen/RISCV/rv32Zbb.ll
===================================================================
--- llvm/test/CodeGen/RISCV/rv32Zbb.ll
+++ llvm/test/CodeGen/RISCV/rv32Zbb.ll
@@ -824,18 +824,14 @@
 ;
 ; RV32IB-LABEL: sextb_i64:
 ; RV32IB:       # %bb.0:
-; RV32IB-NEXT:    sext.b a2, a0
-; RV32IB-NEXT:    slli a0, a0, 24
+; RV32IB-NEXT:    sext.b a0, a0
 ; RV32IB-NEXT:    srai a1, a0, 31
-; RV32IB-NEXT:    mv a0, a2
 ; RV32IB-NEXT:    ret
 ;
 ; RV32IBB-LABEL: sextb_i64:
 ; RV32IBB:       # %bb.0:
-; RV32IBB-NEXT:    sext.b a2, a0
-; RV32IBB-NEXT:    slli a0, a0, 24
+; RV32IBB-NEXT:    sext.b a0, a0
 ; RV32IBB-NEXT:    srai a1, a0, 31
-; RV32IBB-NEXT:    mv a0, a2
 ; RV32IBB-NEXT:    ret
   %shl = shl i64 %a, 56
   %shr = ashr exact i64 %shl, 56
@@ -873,18 +869,14 @@
 ;
 ; RV32IB-LABEL: sexth_i64:
 ; RV32IB:       # %bb.0:
-; RV32IB-NEXT:    sext.h a2, a0
-; RV32IB-NEXT:    slli a0, a0, 16
+; RV32IB-NEXT:    sext.h a0, a0
 ; RV32IB-NEXT:    srai a1, a0, 31
-; RV32IB-NEXT:    mv a0, a2
 ; RV32IB-NEXT:    ret
 ;
 ; RV32IBB-LABEL: sexth_i64:
 ; RV32IBB:       # %bb.0:
-; RV32IBB-NEXT:    sext.h a2, a0
-; RV32IBB-NEXT:    slli a0, a0, 16
+; RV32IBB-NEXT:    sext.h a0, a0
 ; RV32IBB-NEXT:    srai a1, a0, 31
-; RV32IBB-NEXT:    mv a0, a2
 ; RV32IBB-NEXT:    ret
   %shl = shl i64 %a, 48
   %shr = ashr exact i64 %shl, 48
Index: llvm/lib/Target/RISCV/RISCVInstrInfoB.td
===================================================================
--- llvm/lib/Target/RISCV/RISCVInstrInfoB.td
+++ llvm/lib/Target/RISCV/RISCVInstrInfoB.td
@@ -845,15 +845,10 @@
 def : Pat<(ctpop GPR:$rs1), (PCNT GPR:$rs1)>;
 } // Predicates = [HasStdExtZbb]
 
-let Predicates = [HasStdExtZbb, IsRV32] in
-def : Pat<(sra (shl GPR:$rs1, (i32 24)), (i32 24)), (SEXTB GPR:$rs1)>;
-let Predicates = [HasStdExtZbb, IsRV64] in
-def : Pat<(sra (shl GPR:$rs1, (i64 56)), (i64 56)), (SEXTB GPR:$rs1)>;
-
-let Predicates = [HasStdExtZbb, IsRV32] in
-def : Pat<(sra (shl GPR:$rs1, (i32 16)), (i32 16)), (SEXTH GPR:$rs1)>;
-let Predicates = [HasStdExtZbb, IsRV64] in
-def : Pat<(sra (shl GPR:$rs1, (i64 48)), (i64 48)), (SEXTH GPR:$rs1)>;
+let Predicates = [HasStdExtZbb] in {
+def : Pat<(sext_inreg GPR:$rs1, i8), (SEXTB GPR:$rs1)>;
+def : Pat<(sext_inreg GPR:$rs1, i16), (SEXTH GPR:$rs1)>;
+}
 
 let Predicates = [HasStdExtZbb] in {
 def : Pat<(smin GPR:$rs1, GPR:$rs2), (MIN  GPR:$rs1, GPR:$rs2)>;
Index: llvm/lib/Target/RISCV/RISCVISelLowering.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -111,8 +111,11 @@
   setOperationAction(ISD::VACOPY, MVT::Other, Expand);
   setOperationAction(ISD::VAEND, MVT::Other, Expand);
 
-  for (auto VT : {MVT::i1, MVT::i8, MVT::i16})
-    setOperationAction(ISD::SIGN_EXTEND_INREG, VT, Expand);
+  setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i1, Expand);
+  if (!Subtarget.hasStdExtZbb()) {
+    setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i8, Expand);
+    setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i16, Expand);
+  }
 
   if (Subtarget.is64Bit()) {
     setOperationAction(ISD::ADD, MVT::i32, Custom);


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