From 4592e16ebb864d7efafbc7d233e16ed41a98aed2 Mon Sep 17 00:00:00 2001
From: Jeremy Larkin <jeremy.larkin@segment.com>
Date: Fri, 16 Apr 2021 15:12:12 -0700
Subject: [PATCH] operand: allow signed immediates to be matched by IsIMMX
 (#182)

Many of the instruction functions correctly match the size of immediate values, but they only accept unsigned immediates. This PR fixes the operand check functions for intermediate types to also accept the signed variants.

Fixes #181
---
 operand/checks.go      | 20 ++++++++++++--------
 operand/checks_test.go |  6 ++++++
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/operand/checks.go b/operand/checks.go
index 2585479d..28de231d 100644
--- a/operand/checks.go
+++ b/operand/checks.go
@@ -35,26 +35,30 @@ func IsIMM2U(op Op) bool {
 
 // IsIMM8 returns true is op is an 8-bit immediate.
 func IsIMM8(op Op) bool {
-	_, ok := op.(U8)
-	return ok
+	_, uok := op.(U8)
+	_, iok := op.(I8)
+	return uok || iok
 }
 
 // IsIMM16 returns true is op is a 16-bit immediate.
 func IsIMM16(op Op) bool {
-	_, ok := op.(U16)
-	return ok
+	_, uok := op.(U16)
+	_, iok := op.(I16)
+	return uok || iok
 }
 
 // IsIMM32 returns true is op is a 32-bit immediate.
 func IsIMM32(op Op) bool {
-	_, ok := op.(U32)
-	return ok
+	_, uok := op.(U32)
+	_, iok := op.(I32)
+	return uok || iok
 }
 
 // IsIMM64 returns true is op is a 64-bit immediate.
 func IsIMM64(op Op) bool {
-	_, ok := op.(U64)
-	return ok
+	_, uok := op.(U64)
+	_, iok := op.(I64)
+	return uok || iok
 }
 
 // IsAL returns true if op is the AL register.
diff --git a/operand/checks_test.go b/operand/checks_test.go
index f6821edd..1d35df5f 100644
--- a/operand/checks_test.go
+++ b/operand/checks_test.go
@@ -36,6 +36,12 @@ func TestChecks(t *testing.T) {
 
 		{IsIMM64, Imm((1 << 64) - 1), true},
 
+		// Signed Immediates
+		{IsIMM8, I8(-1), true},
+		{IsIMM16, I16(-1), true},
+		{IsIMM32, I32(-1), true},
+		{IsIMM64, I64(-1), true},
+
 		// Specific registers
 		{IsAL, reg.AL, true},
 		{IsAL, reg.CL, false},