Bug 875419 - Fold ImmWord values which fit in 32-bit immediate fields. r=sstangl

js/src/ion/x64/MacroAssembler-x64.h

@@ -387,8 +387,12 @@ class MacroAssemblerX64 : public MacroAssemblerX86Shared
         cmpq(lhs, ScratchReg);
     }
     void cmpPtr(const Operand &lhs, const ImmWord rhs) {
-        mov(rhs, ScratchReg);
-        cmpq(lhs, ScratchReg);
+        if ((intptr_t)rhs.value <= INT32_MAX && (intptr_t)rhs.value >= INT32_MIN) {
+            cmpq(lhs, Imm32((int32_t)rhs.value));
+        } else {
+            mov(rhs, ScratchReg);
+            cmpq(lhs, ScratchReg);
+        }
     }
     void cmpPtr(const Address &lhs, const ImmGCPtr rhs) {
         cmpPtr(Operand(lhs), rhs);
@@ -443,8 +447,12 @@ class MacroAssemblerX64 : public MacroAssemblerX86Shared
     }
     void addPtr(ImmWord imm, const Register &dest) {
         JS_ASSERT(dest != ScratchReg);
-        mov(imm, ScratchReg);
-        addq(ScratchReg, dest);
+        if ((intptr_t)imm.value <= INT32_MAX && (intptr_t)imm.value >= INT32_MIN) {
+            addq(Imm32((int32_t)imm.value), dest);
+        } else {
+            mov(imm, ScratchReg);
+            addq(ScratchReg, dest);
+        }
     }
     void addPtr(const Address &src, const Register &dest) {
         addq(Operand(src), dest);
@@ -554,8 +562,12 @@ class MacroAssemblerX64 : public MacroAssemblerX86Shared
         shlq(Imm32(1), dest);
     }
     void storePtr(ImmWord imm, const Address &address) {
-        mov(imm, ScratchReg);
-        movq(ScratchReg, Operand(address));
+        if ((intptr_t)imm.value <= INT32_MAX && (intptr_t)imm.value >= INT32_MIN) {
+            mov(Imm32((int32_t)imm.value), Operand(address));
+        } else {
+            mov(imm, ScratchReg);
+            movq(ScratchReg, Operand(address));
+        }
     }
     void storePtr(ImmGCPtr imm, const Address &address) {
         movq(imm, ScratchReg);