diff --git a/js/src/assembler/assembler/X86Assembler.h b/js/src/assembler/assembler/X86Assembler.h
index 647b20b8595..0e7ac0cdf4b 100644
--- a/js/src/assembler/assembler/X86Assembler.h
+++ b/js/src/assembler/assembler/X86Assembler.h
@@ -287,6 +287,7 @@ private:
         OP2_XORPD_VpdWpd    = 0x57,
         OP2_MOVD_VdEd       = 0x6E,
         OP2_PSRLDQ_Vd       = 0x73,
+        OP2_PCMPEQW         = 0x75,
         OP2_MOVD_EdVd       = 0x7E,
         OP2_JCC_rel32       = 0x80,
         OP_SETCC            = 0x90,
@@ -675,7 +676,7 @@ public:
 
     void fstp_m(int offset, RegisterID base)
     {
-	m_formatter.oneByteOp(OP_FPU6, FPU6_OP_FSTP, base, offset);
+	   m_formatter.oneByteOp(OP_FPU6, FPU6_OP_FSTP, base, offset);
     }
 
     void negl_r(RegisterID dst)
@@ -2049,6 +2050,15 @@ public:
 
     // SSE operations:
 
+    void pcmpeqw_rr(XMMRegisterID src, XMMRegisterID dst)
+    {
+        js::JaegerSpew(js::JSpew_Insns,
+                       IPFX "pcmpeqw    %s, %s\n", MAYBE_PAD,
+                       nameFPReg(src), nameFPReg(dst));
+        m_formatter.prefix(PRE_SSE_66);
+        m_formatter.twoByteOp(OP2_PCMPEQW, (RegisterID)dst, (RegisterID)src); /* right order ? */
+    }
+
     void addsd_rr(XMMRegisterID src, XMMRegisterID dst)
     {
         js::JaegerSpew(js::JSpew_Insns,
@@ -2185,13 +2195,33 @@ public:
     void psrldq_rr(XMMRegisterID dest, int shift)
     {
         js::JaegerSpew(js::JSpew_Insns,
-                       IPFX "pslldq     %s, %d\n", MAYBE_PAD,
+                       IPFX "psrldq     %s, %d\n", MAYBE_PAD,
                        nameFPReg(dest), shift);
         m_formatter.prefix(PRE_SSE_66);
         m_formatter.twoByteOp(OP2_PSRLDQ_Vd, (RegisterID)3, (RegisterID)dest);
         m_formatter.immediate8(shift);
     }
 
+    void psllq_rr(XMMRegisterID dest, int shift)
+    {
+        js::JaegerSpew(js::JSpew_Insns,
+                       IPFX "psllq     %s, %d\n", MAYBE_PAD,
+                       nameFPReg(dest), shift);
+        m_formatter.prefix(PRE_SSE_66);
+        m_formatter.twoByteOp(OP2_PSRLDQ_Vd, (RegisterID)6, (RegisterID)dest);
+        m_formatter.immediate8(shift);
+    }
+
+    void psrlq_rr(XMMRegisterID dest, int shift)
+    {
+        js::JaegerSpew(js::JSpew_Insns,
+                       IPFX "psrlq     %s, %d\n", MAYBE_PAD,
+                       nameFPReg(dest), shift);
+        m_formatter.prefix(PRE_SSE_66);
+        m_formatter.twoByteOp(OP2_PSRLDQ_Vd, (RegisterID)2, (RegisterID)dest);
+        m_formatter.immediate8(shift);
+    }
+
     void movmskpd_rr(XMMRegisterID src, RegisterID dst)
     {
         js::JaegerSpew(js::JSpew_Insns,
diff --git a/js/src/ion/shared/Assembler-x86-shared.h b/js/src/ion/shared/Assembler-x86-shared.h
index 006b2559c6e..676eab6d20b 100644
--- a/js/src/ion/shared/Assembler-x86-shared.h
+++ b/js/src/ion/shared/Assembler-x86-shared.h
@@ -1007,9 +1007,15 @@ class AssemblerX86Shared
             JS_NOT_REACHED("unexpected operand kind");
         }
     }
-    void psrlq(Imm32 shift, const FloatRegister &dest) {
+    void psrldq(Imm32 shift, const FloatRegister &dest) {
         masm.psrldq_rr(dest.code(), shift.value);
     }
+    void psllq(Imm32 shift, const FloatRegister &dest) {
+        masm.psllq_rr(dest.code(), shift.value);
+    }
+    void psrlq(Imm32 shift, const FloatRegister &dest) {
+        masm.psrlq_rr(dest.code(), shift.value);
+    }
 
     void cvtsi2sd(const Operand &src, const FloatRegister &dest) {
         switch (src.kind()) {
@@ -1042,6 +1048,9 @@ class AssemblerX86Shared
     void ucomisd(const FloatRegister &lhs, const FloatRegister &rhs) {
         masm.ucomisd_rr(rhs.code(), lhs.code());
     }
+    void pcmpeqw(const FloatRegister &lhs, const FloatRegister &rhs) {
+        masm.pcmpeqw_rr(rhs.code(), lhs.code());
+    }    
     void movd(const Register &src, const FloatRegister &dest) {
         masm.movd_rr(src.code(), dest.code());
     }
diff --git a/js/src/ion/shared/MacroAssembler-x86-shared.h b/js/src/ion/shared/MacroAssembler-x86-shared.h
index a383292e9a4..0dd735d5a55 100644
--- a/js/src/ion/shared/MacroAssembler-x86-shared.h
+++ b/js/src/ion/shared/MacroAssembler-x86-shared.h
@@ -323,6 +323,43 @@ class MacroAssemblerX86Shared : public Assembler
         bind(&done);
     }
 
+    bool maybeInlineDouble(uint64_t u, const FloatRegister &dest) {
+        // This implements parts of "13.4 Generating constants" of 
+        // "2. Optimizing subroutines in assembly language" by Agner Fog.
+        switch (u) {
+          case 0:
+            xorpd(dest, dest);
+            break;
+          case 0x3fe0000000000000: // 0.5
+            pcmpeqw(dest, dest);
+            psllq(Imm32(55), dest);
+            psrlq(Imm32(2), dest);
+            break;
+          case 0x3ff0000000000000: // 1.0
+            pcmpeqw(dest, dest);
+            psllq(Imm32(54), dest);
+            psrlq(Imm32(2), dest);
+            break;
+          case 0x3ff8000000000000: // 1.5
+            pcmpeqw(dest, dest);
+            psllq(Imm32(53), dest);
+            psrlq(Imm32(2), dest);
+            break;
+          case 0x4000000000000000: // 2.0
+            pcmpeqw(dest, dest);
+            psllq(Imm32(63), dest);
+            psrlq(Imm32(1), dest);
+            break;
+          case 0xc000000000000000: // -2.0
+            pcmpeqw(dest, dest);
+            psllq(Imm32(62), dest);
+            break;
+          default:
+            return false;
+        }
+        return true;
+    }
+
     // Emit a JMP that can be toggled to a CMP. See ToggleToJmp(), ToggleToCmp().
     CodeOffsetLabel toggledJump(Label *label) {
         CodeOffsetLabel offset(size());
diff --git a/js/src/ion/x64/MacroAssembler-x64.h b/js/src/ion/x64/MacroAssembler-x64.h
index 1780565e3ca..7e296e26885 100644
--- a/js/src/ion/x64/MacroAssembler-x64.h
+++ b/js/src/ion/x64/MacroAssembler-x64.h
@@ -704,9 +704,7 @@ class MacroAssemblerX64 : public MacroAssemblerX86Shared
             double d;
         } pun;
         pun.d = d;
-        if (pun.u == 0) {
-            xorpd(dest, dest);
-        } else {
+        if (!maybeInlineDouble(pun.u, dest)) {
             movq(ImmWord(pun.u), ScratchReg);
             movqsd(ScratchReg, dest);
         }
diff --git a/js/src/ion/x86/CodeGenerator-x86.cpp b/js/src/ion/x86/CodeGenerator-x86.cpp
index d95a54afc34..d6fa169060e 100644
--- a/js/src/ion/x86/CodeGenerator-x86.cpp
+++ b/js/src/ion/x86/CodeGenerator-x86.cpp
@@ -199,10 +199,8 @@ CodeGeneratorX86::visitDouble(LDouble *ins)
     } dpun;
     dpun.d = v.toDouble();
 
-    if (dpun.u == 0) {
-        masm.xorpd(ToFloatRegister(out), ToFloatRegister(out));
+    if (masm.maybeInlineDouble(dpun.u, ToFloatRegister(out)))
         return true;
-    }
 
     DeferredDouble *d = new DeferredDouble(cindex->index());
     if (!deferredDoubles_.append(d))
diff --git a/js/src/ion/x86/MacroAssembler-x86.h b/js/src/ion/x86/MacroAssembler-x86.h
index 6aaddda8946..e42220a056b 100644
--- a/js/src/ion/x86/MacroAssembler-x86.h
+++ b/js/src/ion/x86/MacroAssembler-x86.h
@@ -542,7 +542,7 @@ class MacroAssemblerX86 : public MacroAssemblerX86Shared
     // Note: this function clobbers the source register.
     void boxDouble(const FloatRegister &src, const ValueOperand &dest) {
         movd(src, dest.payloadReg());
-        psrlq(Imm32(4), src);
+        psrldq(Imm32(4), src);
         movd(src, dest.typeReg());
     }
     void unboxInt32(const ValueOperand &src, const Register &dest) {
diff --git a/js/src/jit-test/tests/ion/inline-doubles.js b/js/src/jit-test/tests/ion/inline-doubles.js
new file mode 100644
index 00000000000..34fc6ad15ac
--- /dev/null
+++ b/js/src/jit-test/tests/ion/inline-doubles.js
@@ -0,0 +1,35 @@
+function add0_5 (n) {
+    return n + 0.5;
+}
+
+function add1_0 (n) {
+    return n + 1;
+}
+
+function add1_5 (n) {
+    return n + 1.5;
+}
+
+function add2_0 (n) {
+    return n + 2;
+}
+
+function sub2_0 (n) {
+    return n - 2;
+}
+
+
+var num = 1.5;
+
+function main () {
+    for (var i = 0; i < 10000; i++) {
+        assertEq(add0_5(num), 2);
+        assertEq(add1_0(num), 2.5);
+        assertEq(add1_5(num), 3);
+        assertEq(add2_0(num), 3.5);
+        assertEq(sub2_0(num), -0.5);
+    }
+}
+
+for (var i = 0; i < 1000; i++)
+    main();
\ No newline at end of file