Subzero: Fix emission of 16-bit immediates.

tests_lit/assembler/x86/immediate_encodings.ll

Index: tests_lit/assembler/x86/immediate_encodings.ll
diff --git a/tests_lit/assembler/x86/immediate_encodings.ll b/tests_lit/assembler/x86/immediate_encodings.ll
index 2a9fcb47329c55a71ac80b672c31043df79541d9..a80fe5b0597ca1ac4a7f3958a906042721fdb977 100644
--- a/tests_lit/assembler/x86/immediate_encodings.ll
+++ b/tests_lit/assembler/x86/immediate_encodings.ll
@@ -44,6 +44,67 @@ entry:
 ; CHECK-LABEL: testXor8Imm8NotEAX
 ; CHECK: 80 f{{[1-3]}} 7f xor {{[^a]}}l, 127
 
+define internal i32 @testXor16Imm8(i32 %arg) {
+entry:
+  %arg_i16 = trunc i32 %arg to i16
+  %result_i16 = xor i16 %arg_i16, 127
+  %result = zext i16 %result_i16 to i32
+  ret i32 %result
+}
+; CHECK-LABEL: testXor16Imm8
+; CHECK: 66 83 f0 7f  xor ax, 127
+
+define internal i32 @testXor16Imm8Neg(i32 %arg) {
+entry:
+  %arg_i16 = trunc i32 %arg to i16
+  %result_i16 = xor i16 %arg_i16, -128
+  %result = zext i16 %result_i16 to i32
+  ret i32 %result
+}
+; CHECK-LABEL: testXor16Imm8Neg
+; CHECK: 66 83 f0 80  xor ax, 128
+
+define internal i32 @testXor16Imm16Eax(i32 %arg) {
+entry:
+  %arg_i16 = trunc i32 %arg to i16
+  %tmp = xor i16 %arg_i16, 1024
+  %result_i16 = add i16 %tmp, 1
+  %result = zext i16 %result_i16 to i32
+  ret i32 %result
+}
+; CHECK-LABEL: testXor16Imm16Eax
+; CHECK: 66 35 00 04  xor ax, 1024
+; CHECK-NEXT: add ax, 1
+
+define internal i32 @testXor16Imm16NegEax(i32 %arg) {
+entry:
+  %arg_i16 = trunc i32 %arg to i16
+  %tmp = xor i16 %arg_i16, -256
+  %result_i16 = add i16 %tmp, 1
+  %result = zext i16 %result_i16 to i32
+  ret i32 %result
+}
+; CHECK-LABEL: testXor16Imm16NegEax
+; CHECK: 66 35 00 ff  xor ax, 65280

[Jim Stichnoth, 2014/09/28 18:14:28]

Oddly, this part works correctly in master.

[jvoung (off chromium), 2014/09/29 01:16:56]

I think that llvm-objdump semi-silently ignored the error.

     124:       66 35 00 ff                                     xor     ax,
65280
     12a:       66 83 c0 01                                     add     ax, 1
     12e:       0f b7 c0                                        movzx   eax, ax

124 + 6 bytes is 12a, but it doesn't show the last two bytes! The llvm-objdump
does print the warning:

  
/...native_client/toolchain_build/out/llvm_x86_64_linux_work/Release+Asserts/bin/llvm-objdump:
warning: invalid instruction encoding

+; CHECK-NEXT: add ax, 1
+
+define internal i32 @testXor16Imm16NotEAX(i32 %arg_i32, i32 %arg2_i32, i32 %arg3_i32) {
+entry:
+  %arg = trunc i32 %arg_i32 to i16
+  %arg2 = trunc i32 %arg2_i32 to i16
+  %arg3 = trunc i32 %arg3_i32 to i16
+  %x = xor i16 %arg, 32767
+  %x2 = xor i16 %arg2, 32767
+  %x3 = xor i16 %arg3, 32767
+  %add1 = add i16 %x, %x2
+  %add2 = add i16 %add1, %x3
+  %result = zext i16 %add2 to i32
+  ret i32 %result
+}
+; CHECK-LABEL: testXor16Imm16NotEAX
+; CHECK: 66 81 f{{[1-3]}} ff 7f  xor {{[^a]}}x, 32767
+; CHECK-NEXT: 66 81 f{{[1-3]}} ff 7f  xor {{[^a]}}x, 32767
+
 define internal i32 @testXor32Imm8(i32 %arg) {
 entry:
   %result = xor i32 %arg, 127