Subzero: Strength-reduce mul by certain constants.

tests_lit/llvm2ice_tests/strength-reduce.ll

+; This tests various strength reduction operations.
+
+; RUN: %if --need=target_X8632 --command %p2i --filetype=obj --disassemble \
+; RUN:   --target x8632 -i %s --args -O2 \
+; RUN:   | %if --need=target_X8632 --command FileCheck %s
+
+define internal i32 @mul_i32_arg_5(i32 %arg) {
+  %result = mul i32 %arg, 5
+  ret i32 %result
+}
+; CHECK-LABEL: mul_i32_arg_5
+; CHECK: lea [[REG:e..]],{{\[}}[[REG]]+[[REG]]*4]
+
+define internal i32 @mul_i32_5_arg(i32 %arg) {
+  %result = mul i32 5, %arg
+  ret i32 %result
+}
+; CHECK-LABEL: mul_i32_5_arg
+; CHECK: lea [[REG:e..]],{{\[}}[[REG]]+[[REG]]*4]
+
+define internal i32 @mul_i32_arg_18(i32 %arg) {
+  %result = mul i32 %arg, 18
+  ret i32 %result
+}
+; CHECK-LABEL: mul_i32_arg_18
+; CHECK-DAG: lea [[REG:e..]],{{\[}}[[REG]]+[[REG]]*8]
+; CHECK-DAG: shl [[REG]],1
+
+define internal i32 @mul_i32_arg_27(i32 %arg) {
+  %result = mul i32 %arg, 27
+  ret i32 %result
+}
+; CHECK-LABEL: mul_i32_arg_27
+; CHECK-DAG: lea [[REG:e..]],{{\[}}[[REG]]+[[REG]]*2]
+; CHECK-DAG: lea [[REG]],{{\[}}[[REG]]+[[REG]]*8]
+
+define internal i32 @mul_i32_arg_m45(i32 %arg) {
+  %result = mul i32 %arg, -45
+  ret i32 %result
+}
+; CHECK-LABEL: mul_i32_arg_m45
+; CHECK-DAG: lea [[REG:e..]],{{\[}}[[REG]]+[[REG]]*8]
+; CHECK-DAG: lea [[REG]],{{\[}}[[REG]]+[[REG]]*4]
+; CHECK: neg [[REG]]
+
+define internal i16 @mul_i16_arg_18(i16 %arg) {
+  %result = mul i16 %arg, 18
+  ret i16 %result
+}
+; Disassembly will look like "lea ax,[eax+eax*8]".
+; CHECK-LABEL: mul_i16_arg_18
+; CHECK-DAG: lea [[REG:..]],{{\[}}e[[REG]]+e[[REG]]*8]
+; CHECK-DAG: shl [[REG]],1
+
+define internal i8 @mul_i8_arg_16(i8 %arg) {
+  %result = mul i8 %arg, 16
+  ret i8 %result
+}
+; CHECK-LABEL: mul_i8_arg_16
+; CHECK: shl {{.*}},0x4
+
+define internal i8 @mul_i8_arg_18(i8 %arg) {
+  %result = mul i8 %arg, 18
+  ret i8 %result
+}
+; CHECK-LABEL: mul_i8_arg_18
+; CHECK: imul