[RISCV] Optimize mul in the zba extension with SH*ADD

This patch makes the following optimization, if the immediate multiplier is not a simm12. (mul x, (power_of_2 + 2)) => (SH1ADD x, (SLLI x, bits)) (mul x, (power_of_2 + 4)) => (SH2ADD x, (SLLI x, bits)) (mul x, (power_of_2 + 8)) => (SH3ADD x, (SLLI x, bits)) Reviewed By: craig.topper Differential Revision: https://reviews.llvm.org/D106648
llvm · Jul 29, 2021 · 264b8e2 · 264b8e2
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commit 264b8e2
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Showing 3 changed files with 29 additions and 36 deletions.
diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -8941,6 +8941,11 @@ bool RISCVTargetLowering::decomposeMulByConstant(LLVMContext &Context, EVT VT,
       if ((Imm + 1).isPowerOf2() || (Imm - 1).isPowerOf2() ||
           (1 - Imm).isPowerOf2() || (-1 - Imm).isPowerOf2())
         return true;
+      // Optimize the MUL to (SH*ADD x, (SLLI x, bits)) if Imm is not simm12.
+      if (Subtarget.hasStdExtZba() && !Imm.isSignedIntN(12) &&
+          ((Imm - 2).isPowerOf2() || (Imm - 4).isPowerOf2() ||
+           (Imm - 8).isPowerOf2()))
+        return true;
       // Omit the following optimization if the sub target has the M extension
       // and the data size >= XLen.
       if (Subtarget.hasStdExtM() && VT.getSizeInBits() >= Subtarget.getXLen())

diff --git a/llvm/test/CodeGen/RISCV/rv32zba.ll b/llvm/test/CodeGen/RISCV/rv32zba.ll
@@ -615,16 +615,14 @@ define i32 @mul4098(i32 %a) {
 ;
 ; RV32IB-LABEL: mul4098:
 ; RV32IB:       # %bb.0:
-; RV32IB-NEXT:    lui a1, 1
-; RV32IB-NEXT:    addi a1, a1, 2
-; RV32IB-NEXT:    mul a0, a0, a1
+; RV32IB-NEXT:    slli a1, a0, 12
+; RV32IB-NEXT:    sh1add a0, a0, a1
 ; RV32IB-NEXT:    ret
 ;
 ; RV32IBA-LABEL: mul4098:
 ; RV32IBA:       # %bb.0:
-; RV32IBA-NEXT:    lui a1, 1
-; RV32IBA-NEXT:    addi a1, a1, 2
-; RV32IBA-NEXT:    mul a0, a0, a1
+; RV32IBA-NEXT:    slli a1, a0, 12
+; RV32IBA-NEXT:    sh1add a0, a0, a1
 ; RV32IBA-NEXT:    ret
   %c = mul i32 %a, 4098
   ret i32 %c
@@ -640,16 +638,14 @@ define i32 @mul4100(i32 %a) {
 ;
 ; RV32IB-LABEL: mul4100:
 ; RV32IB:       # %bb.0:
-; RV32IB-NEXT:    lui a1, 1
-; RV32IB-NEXT:    addi a1, a1, 4
-; RV32IB-NEXT:    mul a0, a0, a1
+; RV32IB-NEXT:    slli a1, a0, 12
+; RV32IB-NEXT:    sh2add a0, a0, a1
 ; RV32IB-NEXT:    ret
 ;
 ; RV32IBA-LABEL: mul4100:
 ; RV32IBA:       # %bb.0:
-; RV32IBA-NEXT:    lui a1, 1
-; RV32IBA-NEXT:    addi a1, a1, 4
-; RV32IBA-NEXT:    mul a0, a0, a1
+; RV32IBA-NEXT:    slli a1, a0, 12
+; RV32IBA-NEXT:    sh2add a0, a0, a1
 ; RV32IBA-NEXT:    ret
   %c = mul i32 %a, 4100
   ret i32 %c
@@ -665,16 +661,14 @@ define i32 @mul4104(i32 %a) {
 ;
 ; RV32IB-LABEL: mul4104:
 ; RV32IB:       # %bb.0:
-; RV32IB-NEXT:    lui a1, 1
-; RV32IB-NEXT:    addi a1, a1, 8
-; RV32IB-NEXT:    mul a0, a0, a1
+; RV32IB-NEXT:    slli a1, a0, 12
+; RV32IB-NEXT:    sh3add a0, a0, a1
 ; RV32IB-NEXT:    ret
 ;
 ; RV32IBA-LABEL: mul4104:
 ; RV32IBA:       # %bb.0:
-; RV32IBA-NEXT:    lui a1, 1
-; RV32IBA-NEXT:    addi a1, a1, 8
-; RV32IBA-NEXT:    mul a0, a0, a1
+; RV32IBA-NEXT:    slli a1, a0, 12
+; RV32IBA-NEXT:    sh3add a0, a0, a1
 ; RV32IBA-NEXT:    ret
   %c = mul i32 %a, 4104
   ret i32 %c

diff --git a/llvm/test/CodeGen/RISCV/rv64zba.ll b/llvm/test/CodeGen/RISCV/rv64zba.ll
@@ -1120,16 +1120,14 @@ define i64 @mul4098(i64 %a) {
 ;
 ; RV64IB-LABEL: mul4098:
 ; RV64IB:       # %bb.0:
-; RV64IB-NEXT:    lui a1, 1
-; RV64IB-NEXT:    addiw a1, a1, 2
-; RV64IB-NEXT:    mul a0, a0, a1
+; RV64IB-NEXT:    slli a1, a0, 12
+; RV64IB-NEXT:    sh1add a0, a0, a1
 ; RV64IB-NEXT:    ret
 ;
 ; RV64IBA-LABEL: mul4098:
 ; RV64IBA:       # %bb.0:
-; RV64IBA-NEXT:    lui a1, 1
-; RV64IBA-NEXT:    addiw a1, a1, 2
-; RV64IBA-NEXT:    mul a0, a0, a1
+; RV64IBA-NEXT:    slli a1, a0, 12
+; RV64IBA-NEXT:    sh1add a0, a0, a1
 ; RV64IBA-NEXT:    ret
   %c = mul i64 %a, 4098
   ret i64 %c
@@ -1145,16 +1143,14 @@ define i64 @mul4100(i64 %a) {
 ;
 ; RV64IB-LABEL: mul4100:
 ; RV64IB:       # %bb.0:
-; RV64IB-NEXT:    lui a1, 1
-; RV64IB-NEXT:    addiw a1, a1, 4
-; RV64IB-NEXT:    mul a0, a0, a1
+; RV64IB-NEXT:    slli a1, a0, 12
+; RV64IB-NEXT:    sh2add a0, a0, a1
 ; RV64IB-NEXT:    ret
 ;
 ; RV64IBA-LABEL: mul4100:
 ; RV64IBA:       # %bb.0:
-; RV64IBA-NEXT:    lui a1, 1
-; RV64IBA-NEXT:    addiw a1, a1, 4
-; RV64IBA-NEXT:    mul a0, a0, a1
+; RV64IBA-NEXT:    slli a1, a0, 12
+; RV64IBA-NEXT:    sh2add a0, a0, a1
 ; RV64IBA-NEXT:    ret
   %c = mul i64 %a, 4100
   ret i64 %c
@@ -1170,16 +1166,14 @@ define i64 @mul4104(i64 %a) {
 ;
 ; RV64IB-LABEL: mul4104:
 ; RV64IB:       # %bb.0:
-; RV64IB-NEXT:    lui a1, 1
-; RV64IB-NEXT:    addiw a1, a1, 8
-; RV64IB-NEXT:    mul a0, a0, a1
+; RV64IB-NEXT:    slli a1, a0, 12
+; RV64IB-NEXT:    sh3add a0, a0, a1
 ; RV64IB-NEXT:    ret
 ;
 ; RV64IBA-LABEL: mul4104:
 ; RV64IBA:       # %bb.0:
-; RV64IBA-NEXT:    lui a1, 1
-; RV64IBA-NEXT:    addiw a1, a1, 8
-; RV64IBA-NEXT:    mul a0, a0, a1
+; RV64IBA-NEXT:    slli a1, a0, 12
+; RV64IBA-NEXT:    sh3add a0, a0, a1
 ; RV64IBA-NEXT:    ret
   %c = mul i64 %a, 4104
   ret i64 %c