[RISCV] Add coverage for strength reduction of mul by small negative immediates

Author: preames

llvm/test/CodeGen/RISCV/rv32zba.ll

@@ -645,3 +645,96 @@ define i32 @addshl_5_8(i32 %a, i32 %b) {
   %e = add i32 %c, %d
   ret i32 %e
 }
+
+define i32 @mul_neg1(i32 %a) {
+; CHECK-LABEL: mul_neg1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    neg a0, a0
+; CHECK-NEXT:    ret
+  %c = mul i32 %a, -1
+  ret i32 %c
+}
+
+define i32 @mul_neg2(i32 %a) {
+; CHECK-LABEL: mul_neg2:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    slli a0, a0, 1
+; CHECK-NEXT:    neg a0, a0
+; CHECK-NEXT:    ret
+  %c = mul i32 %a, -2
+  ret i32 %c
+}
+
+define i32 @mul_neg3(i32 %a) {
+; RV32I-LABEL: mul_neg3:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    slli a1, a0, 1
+; RV32I-NEXT:    neg a0, a0
+; RV32I-NEXT:    sub a0, a0, a1
+; RV32I-NEXT:    ret
+;
+; RV32ZBA-LABEL: mul_neg3:
+; RV32ZBA:       # %bb.0:
+; RV32ZBA-NEXT:    sh1add a0, a0, a0
+; RV32ZBA-NEXT:    neg a0, a0
+; RV32ZBA-NEXT:    ret
+  %c = mul i32 %a, -3
+  ret i32 %c
+}
+
+define i32 @mul_neg4(i32 %a) {
+; CHECK-LABEL: mul_neg4:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    slli a0, a0, 2
+; CHECK-NEXT:    neg a0, a0
+; CHECK-NEXT:    ret
+  %c = mul i32 %a, -4
+  ret i32 %c
+}
+
+define i32 @mul_neg5(i32 %a) {
+; RV32I-LABEL: mul_neg5:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    slli a1, a0, 2
+; RV32I-NEXT:    neg a0, a0
+; RV32I-NEXT:    sub a0, a0, a1
+; RV32I-NEXT:    ret
+;
+; RV32ZBA-LABEL: mul_neg5:
+; RV32ZBA:       # %bb.0:
+; RV32ZBA-NEXT:    sh2add a0, a0, a0
+; RV32ZBA-NEXT:    neg a0, a0
+; RV32ZBA-NEXT:    ret
+  %c = mul i32 %a, -5
+  ret i32 %c
+}
+
+define i32 @mul_neg6(i32 %a) {
+; CHECK-LABEL: mul_neg6:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    li a1, -6
+; CHECK-NEXT:    mul a0, a0, a1
+; CHECK-NEXT:    ret
+  %c = mul i32 %a, -6
+  ret i32 %c
+}
+
+define i32 @mul_neg7(i32 %a) {
+; CHECK-LABEL: mul_neg7:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    slli a1, a0, 3
+; CHECK-NEXT:    sub a0, a0, a1
+; CHECK-NEXT:    ret
+  %c = mul i32 %a, -7
+  ret i32 %c
+}
+
+define i32 @mul_neg8(i32 %a) {
+; CHECK-LABEL: mul_neg8:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    slli a0, a0, 3
+; CHECK-NEXT:    neg a0, a0
+; CHECK-NEXT:    ret
+  %c = mul i32 %a, -8
+  ret i32 %c
+}

llvm/test/CodeGen/RISCV/rv64zba.ll

@@ -2533,3 +2533,96 @@ define i64 @regression(i32 signext %x, i32 signext %y) {
   %res = mul nuw nsw i64 %ext, 24
   ret i64 %res
 }
+
+define i64 @mul_neg1(i64 %a) {
+; CHECK-LABEL: mul_neg1:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    neg a0, a0
+; CHECK-NEXT:    ret
+  %c = mul i64 %a, -1
+  ret i64 %c
+}
+
+define i64 @mul_neg2(i64 %a) {
+; CHECK-LABEL: mul_neg2:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    slli a0, a0, 1
+; CHECK-NEXT:    neg a0, a0
+; CHECK-NEXT:    ret
+  %c = mul i64 %a, -2
+  ret i64 %c
+}
+
+define i64 @mul_neg3(i64 %a) {
+; RV64I-LABEL: mul_neg3:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    slli a1, a0, 1
+; RV64I-NEXT:    neg a0, a0
+; RV64I-NEXT:    sub a0, a0, a1
+; RV64I-NEXT:    ret
+;
+; RV64ZBA-LABEL: mul_neg3:
+; RV64ZBA:       # %bb.0:
+; RV64ZBA-NEXT:    sh1add a0, a0, a0
+; RV64ZBA-NEXT:    neg a0, a0
+; RV64ZBA-NEXT:    ret
+  %c = mul i64 %a, -3
+  ret i64 %c
+}
+
+define i64 @mul_neg4(i64 %a) {
+; CHECK-LABEL: mul_neg4:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    slli a0, a0, 2
+; CHECK-NEXT:    neg a0, a0
+; CHECK-NEXT:    ret
+  %c = mul i64 %a, -4
+  ret i64 %c
+}
+
+define i64 @mul_neg5(i64 %a) {
+; RV64I-LABEL: mul_neg5:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    slli a1, a0, 2
+; RV64I-NEXT:    neg a0, a0
+; RV64I-NEXT:    sub a0, a0, a1
+; RV64I-NEXT:    ret
+;
+; RV64ZBA-LABEL: mul_neg5:
+; RV64ZBA:       # %bb.0:
+; RV64ZBA-NEXT:    sh2add a0, a0, a0
+; RV64ZBA-NEXT:    neg a0, a0
+; RV64ZBA-NEXT:    ret
+  %c = mul i64 %a, -5
+  ret i64 %c
+}
+
+define i64 @mul_neg6(i64 %a) {
+; CHECK-LABEL: mul_neg6:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    li a1, -6
+; CHECK-NEXT:    mul a0, a0, a1
+; CHECK-NEXT:    ret
+  %c = mul i64 %a, -6
+  ret i64 %c
+}
+
+define i64 @mul_neg7(i64 %a) {
+; CHECK-LABEL: mul_neg7:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    slli a1, a0, 3
+; CHECK-NEXT:    sub a0, a0, a1
+; CHECK-NEXT:    ret
+  %c = mul i64 %a, -7
+  ret i64 %c
+}
+
+define i64 @mul_neg8(i64 %a) {
+; CHECK-LABEL: mul_neg8:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    slli a0, a0, 3
+; CHECK-NEXT:    neg a0, a0
+; CHECK-NEXT:    ret
+  %c = mul i64 %a, -8
+  ret i64 %c
+}