[llvm] 7f811ce - [RISCV] Optimize (sext.w, srli) to sraiw with Zba.

[Chenbing Zheng via llvm-commits]

Author: Chenbing Zheng
Date: 2022-02-28T10:34:35+08:00
New Revision: 7f811ce12744db67e9d6450541c6bd313e06db59

URL: https://github.com/llvm/llvm-project/commit/7f811ce12744db67e9d6450541c6bd313e06db59
DIFF: https://github.com/llvm/llvm-project/commit/7f811ce12744db67e9d6450541c6bd313e06db59.diff

LOG: [RISCV] Optimize (sext.w, srli) to sraiw with Zba.

In this patch, we add a more narrower exclusion for
zeroext (srl x) -> srli (slli x), so that it provides an opportunity
for the selection of sraiw.

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D120467

Added: 
    

Modified: 
    llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
    llvm/test/CodeGen/RISCV/rv64i-exhaustive-w-insts.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp b/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
index 88eeca01d9ac1..06e32eb2827aa 100644
--- a/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
@@ -772,7 +772,10 @@ void RISCVDAGToDAGISel::Select(SDNode *Node) {
         }
 
         // (srli (slli x, c3-c2), c3).
-        if (OneUseOrZExtW && !IsANDI) {
+        // Skip it in order to select sraiw.
+        bool Skip = Subtarget->hasStdExtZba() && C3 == 32 &&
+                    X.getOpcode() == ISD::SIGN_EXTEND_INREG;
+        if (OneUseOrZExtW && !IsANDI && !Skip) {
           SDNode *SLLI = CurDAG->getMachineNode(
               RISCV::SLLI, DL, XLenVT, X,
               CurDAG->getTargetConstant(C3 - C2, DL, XLenVT));

diff  --git a/llvm/test/CodeGen/RISCV/rv64i-exhaustive-w-insts.ll b/llvm/test/CodeGen/RISCV/rv64i-exhaustive-w-insts.ll
index 777c814813cff..22791dd99465e 100644
--- a/llvm/test/CodeGen/RISCV/rv64i-exhaustive-w-insts.ll
+++ b/llvm/test/CodeGen/RISCV/rv64i-exhaustive-w-insts.ll
@@ -1935,14 +1935,19 @@ define signext i32 @sext_sraiw_zext(i32 zeroext %a) nounwind {
   ret i32 %1
 }
 
-; TODO: The sext.w+srli can be replaced with sraiw with Zba.
 define zeroext i32 @zext_sraiw_aext(i32 %a) nounwind {
-; RV64-LABEL: zext_sraiw_aext:
-; RV64:       # %bb.0:
-; RV64-NEXT:    sext.w a0, a0
-; RV64-NEXT:    slli a0, a0, 25
-; RV64-NEXT:    srli a0, a0, 32
-; RV64-NEXT:    ret
+; RV64I-LABEL: zext_sraiw_aext:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    sext.w a0, a0
+; RV64I-NEXT:    slli a0, a0, 25
+; RV64I-NEXT:    srli a0, a0, 32
+; RV64I-NEXT:    ret
+;
+; RV64ZBA-LABEL: zext_sraiw_aext:
+; RV64ZBA:       # %bb.0:
+; RV64ZBA-NEXT:    sraiw a0, a0, 7
+; RV64ZBA-NEXT:    zext.w a0, a0
+; RV64ZBA-NEXT:    ret
   %1 = ashr i32 %a, 7
   ret i32 %1
 }
@@ -1957,14 +1962,19 @@ define zeroext i32 @zext_sraiw_sext(i32 signext %a) nounwind {
   ret i32 %1
 }
 
-; TODO: The sext.w+srli can be replaced with sraiw with Zba.
 define zeroext i32 @zext_sraiw_zext(i32 zeroext %a) nounwind {
-; RV64-LABEL: zext_sraiw_zext:
-; RV64:       # %bb.0:
-; RV64-NEXT:    sext.w a0, a0
-; RV64-NEXT:    slli a0, a0, 23
-; RV64-NEXT:    srli a0, a0, 32
-; RV64-NEXT:    ret
+; RV64I-LABEL: zext_sraiw_zext:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    sext.w a0, a0
+; RV64I-NEXT:    slli a0, a0, 23
+; RV64I-NEXT:    srli a0, a0, 32
+; RV64I-NEXT:    ret
+;
+; RV64ZBA-LABEL: zext_sraiw_zext:
+; RV64ZBA:       # %bb.0:
+; RV64ZBA-NEXT:    sraiw a0, a0, 9
+; RV64ZBA-NEXT:    zext.w a0, a0
+; RV64ZBA-NEXT:    ret
   %1 = ashr i32 %a, 9
   ret i32 %1
 }