Subzero: Strength-reduce mul by certain constants.

tests_lit/assembler/x86/immediate_encodings.ll

 ; Tests various aspects of x86 immediate encoding. Some encodings are shorter.
 ; For example, the encoding is shorter for 8-bit immediates or when using EAX.
 ; This assumes that EAX is chosen as the first free register in O2 mode.
 
 ; RUN: %p2i --filetype=obj --disassemble -i %s --args -O2 | FileCheck %s
 
 define internal i32 @testXor8Imm8(i32 %arg) {
 entry:
   %arg_i8 = trunc i32 %arg to i8
   %result_i8 = xor i8 %arg_i8, 127
@@ skipping 179 matching lines @@
   %result = zext i16 %result_i16 to i32
   ret i32 %result
 }
 ; CHECK-LABEL: testMul16Imm8Neg
 ; CHECK: 66 6b c0 91  imul ax,ax
 ; CHECK-NEXT: add ax,0x1
 
 define internal i32 @testMul16Imm16(i32 %arg) {
 entry:
   %arg_i16 = trunc i32 %arg to i16
-  %tmp = mul i16 %arg_i16, 1024
+  %tmp = mul i16 %arg_i16, 1025
   %result_i16 = add i16 %tmp, 1
   %result = zext i16 %result_i16 to i32
   ret i32 %result
 }
 ; CHECK-LABEL: testMul16Imm16
-; CHECK: 66 69 c0 00 04  imul ax,ax
+; CHECK: 66 69 c0 01 04  imul ax,ax
 ; CHECK-NEXT: add ax,0x1
 
 define internal i32 @testMul16Imm16Neg(i32 %arg) {
 entry:
   %arg_i16 = trunc i32 %arg to i16
-  %tmp = mul i16 %arg_i16, -256
+  %tmp = mul i16 %arg_i16, -255
   %result_i16 = add i16 %tmp, 1
   %result = zext i16 %result_i16 to i32
   ret i32 %result
 }
 ; CHECK-LABEL: testMul16Imm16Neg
-; CHECK: 66 69 c0 00 ff  imul ax,ax
+; CHECK: 66 69 c0 01 ff  imul ax,ax,0xff01
 ; CHECK-NEXT: add ax,0x1
 
 define internal i32 @testMul32Imm8(i32 %arg) {
 entry:
   %result = mul i32 %arg, 99
   ret i32 %result
 }
 ; CHECK-LABEL: testMul32Imm8
 ; CHECK: 6b c0 63  imul eax,eax
 
 define internal i32 @testMul32Imm8Neg(i32 %arg) {
 entry:
   %result = mul i32 %arg, -111
   ret i32 %result
 }
 ; CHECK-LABEL: testMul32Imm8Neg
 ; CHECK: 6b c0 91  imul eax,eax
 
 define internal i32 @testMul32Imm16(i32 %arg) {
 entry:
-  %result = mul i32 %arg, 1024
+  %result = mul i32 %arg, 1025
   ret i32 %result
 }
 ; CHECK-LABEL: testMul32Imm16
-; CHECK: 69 c0 00 04 00 00  imul eax,eax
+; CHECK: 69 c0 01 04 00 00  imul eax,eax
 
 define internal i32 @testMul32Imm16Neg(i32 %arg) {
 entry:
-  %result = mul i32 %arg, -256
+  %result = mul i32 %arg, -255
   ret i32 %result
 }
 ; CHECK-LABEL: testMul32Imm16Neg
-; CHECK: 69 c0 00 ff ff ff  imul eax,eax
+; CHECK: 69 c0 01 ff ff ff  imul eax,eax,0xffffff01
 
 ; The GPR shift instructions either allow an 8-bit immediate or
 ; have a special encoding for "1".
 define internal i32 @testShl16Imm8(i32 %arg) {
 entry:
   %arg_i16 = trunc i32 %arg to i16
   %tmp = shl i16 %arg_i16, 13
   %result = zext i16 %tmp to i32
   ret i32 %result
 }
@@ skipping 37 matching lines @@
   %r4 = call i64 @llvm.ctlz.i64(i64 %w, i1 false)
   %res1 = add i64 %r, %r2
   %res2 = add i64 %r3, %r4
   %res = add i64 %res1, %res2
   ret i64 %res
 }
 ; CHECK-LABEL: test_via_ctlz_64
 ; CHECK-DAG: 85 c0 test eax,eax
 ; CHECK-DAG: 85 db test ebx,ebx
 ; CHECK-DAG: 85 f6 test esi,esi