[llvm] [RISCV] Don't select sh{1, 2, 3}add if shl doesn't have one use (PR #143351)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-risc-v

Author: Jim Lin (tclin914)

<details>
<summary>Changes</summary>

Try to fix https://github.com/llvm/llvm-project/pull/130829#pullrequestreview-2730533158. There's no benefit if shl doesn't have one use.

---
Full diff: https://github.com/llvm/llvm-project/pull/143351.diff


2 Files Affected:

- (modified) llvm/lib/Target/RISCV/RISCVISelLowering.cpp (+3) 
- (modified) llvm/test/CodeGen/RISCV/reassoc-shl-addi-add.ll (+11-12) 


``````````diff
diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index 1cbd3f4233eee..4cf9a9fb7f969 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -14887,6 +14887,9 @@ static SDValue combineShlAddIAddImpl(SDNode *N, SDValue AddI, SDValue Other,
   if (!sd_match(SHLVal, m_BinOp(ISD::SHL, m_Value(), m_ConstInt(VShift))))
     return SDValue();
 
+  if (!SHLVal.hasOneUse())
+    return SDValue();
+
   if (VShift.slt(1) || VShift.sgt(3))
     return SDValue();
 
diff --git a/llvm/test/CodeGen/RISCV/reassoc-shl-addi-add.ll b/llvm/test/CodeGen/RISCV/reassoc-shl-addi-add.ll
index 88ab1c0c3eaef..baa9011802dac 100644
--- a/llvm/test/CodeGen/RISCV/reassoc-shl-addi-add.ll
+++ b/llvm/test/CodeGen/RISCV/reassoc-shl-addi-add.ll
@@ -8,10 +8,10 @@ declare i32 @callee(i32 noundef, i32 noundef, i32 noundef, i32 noundef)
 define void @t1(i32 noundef %a, i32 noundef %b, i32 noundef %c, i32 noundef %d) #0 {
 ; CHECK-LABEL: t1:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    sh2add a2, a0, a2
-; CHECK-NEXT:    sh2add a1, a0, a1
-; CHECK-NEXT:    addi a1, a1, 45
-; CHECK-NEXT:    addi a2, a2, 45
+; CHECK-NEXT:    slli a4, a0, 2
+; CHECK-NEXT:    addi a4, a4, 45
+; CHECK-NEXT:    add a1, a4, a1
+; CHECK-NEXT:    add a2, a4, a2
 ; CHECK-NEXT:    sh2add a3, a0, a3
 ; CHECK-NEXT:    mv a0, a1
 ; CHECK-NEXT:    tail callee
@@ -133,12 +133,11 @@ entry:
 define void @t8(i32 noundef %a, i32 noundef %b, i32 noundef %c, i32 noundef %d) #0 {
 ; CHECK-LABEL: t8:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    sh3add a2, a0, a2
-; CHECK-NEXT:    sh3add a1, a0, a1
 ; CHECK-NEXT:    lui a4, 1
 ; CHECK-NEXT:    addi a4, a4, 1307
-; CHECK-NEXT:    add a1, a1, a4
-; CHECK-NEXT:    add a2, a2, a4
+; CHECK-NEXT:    sh3add a4, a0, a4
+; CHECK-NEXT:    add a1, a4, a1
+; CHECK-NEXT:    add a2, a4, a2
 ; CHECK-NEXT:    sh3add a3, a0, a3
 ; CHECK-NEXT:    mv a0, a1
 ; CHECK-NEXT:    tail callee
@@ -155,10 +154,10 @@ entry:
 define void @t9(i32 noundef %a, i32 noundef %b, i32 noundef %c, i32 noundef %d) #0 {
 ; CHECK-LABEL: t9:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    sh2add a2, a0, a2
-; CHECK-NEXT:    sh2add a1, a0, a1
-; CHECK-NEXT:    addi a1, a1, -42
-; CHECK-NEXT:    addi a2, a2, -42
+; CHECK-NEXT:    slli a4, a0, 2
+; CHECK-NEXT:    addi a4, a4, -42
+; CHECK-NEXT:    add a1, a4, a1
+; CHECK-NEXT:    add a2, a4, a2
 ; CHECK-NEXT:    sh2add a3, a0, a3
 ; CHECK-NEXT:    mv a0, a1
 ; CHECK-NEXT:    tail callee

``````````

</details>


https://github.com/llvm/llvm-project/pull/143351