Update comments in VMAC

1 files changed, 15 insertions, 15 deletions

diff --git a/vmac.cpp b/vmac.cpp
index 2d1ddfee..5dd550ac 100644
--- a/vmac.cpp
+++ b/vmac.cpp
@@ -186,31 +186,32 @@ void VMAC_Base::VHASH_Update_SSE2(const word64 *data, size_t blocksRemainingInWo
 	const word64 *nhK = m_nhKey();

 	word64 *polyS = (word64*)(void*)m_polyState();

 	word32 L1KeyLength = m_L1KeyLength;

+	word32 temp;

 

 	// These are used in the ASM, but some analysis services miss it.

 	CRYPTOPP_UNUSED(data); CRYPTOPP_UNUSED(tagPart);

-	CRYPTOPP_UNUSED(L1KeyLength);

+	CRYPTOPP_UNUSED(L1KeyLength); CRYPTOPP_UNUSED(temp);

 	CRYPTOPP_UNUSED(blocksRemainingInWord64);

 

-	// This inline ASM is tricky, and down right difficult when PIC is

-	// in effect. The ASM uses all the general purpose registers and all

-	// the XMM registers on 32-bit machines. When PIC is in effect on a

-	// 32-bit machine, GCC uses EBX as a base register. Saving EBX with

-	// 'mov %%ebx, %0' and restoring EBX with 'mov %0, %%ebx' causes GCC

-	// to generate 'mov -0x40(%ebx), %ebx' for the restore. That obviously

-	// won't work because EBX is no longer accurate. We can push and pop

-	// EBX, but that breaks stack-based references. Attempting to sidestep

-	// the issues with clobber lists results in "error: ‘asm’ operand has

+	// This inline ASM is tricky, and down right difficult on 32-bit when

+	// PIC is in effect. The ASM uses all the general purpose registers

+	// and all the XMM registers on 32-bit machines. When PIC is in effect

+	// on a 32-bit machine, GCC uses EBX as a base register for PLT. Saving

+	// EBX with 'mov %%ebx, %0' and restoring EBX with 'mov %0, %%ebx'

+	// causes GCC to generate 'mov -0x40(%ebx), %ebx' for the restore. That

+	// obviously won't work because EBX is no longer valid. We can push and

+	// pop EBX, but that breaks the stack-based references. Attempting to

+	// sidestep with clobber lists results in "error: ‘asm’ operand has

 	// impossible constraints". Eventually, we found we could save EBX to

 	// ESP-20, which is one word below our stack in the frame.

 #ifdef __GNUC__

 	__asm__ __volatile__

 	(

 # if defined(__i386__) || defined(__i686__)

-    // Save EBX for PIC

+	// Save EBX for PIC

 	AS2(	mov 	%%ebx, -20(%%esp))

 # endif

-	AS2(	mov 	%0, %%ebx)  // L1KeyLength

+	AS2(	mov 	%0, %%ebx)  // L1KeyLength into EBX

 	INTEL_NOPREFIX

 #else

 	#if defined(__INTEL_COMPILER)

@@ -325,6 +326,7 @@ void VMAC_Base::VHASH_Update_SSE2(const word64 *data, size_t blocksRemainingInWo
 #define k1 [eax+2*8+3*4]

 #define k2 [eax+2*8+0*4]

 #define k3 [eax+2*8+1*4]

+

 	AS2(	test	dl, dl)

 	ASJ(	jz,		2, f)

 	AS2(	movd	mm1, k0)

@@ -413,6 +415,7 @@ void VMAC_Base::VHASH_Update_SSE2(const word64 *data, size_t blocksRemainingInWo
 	AS2(	por		mm4, mm7)

 	AS2(	paddq	mm0, mm4)

 	AS2(	movq	a2, mm0)

+

 #undef a0

 #undef a1

 #undef a2

@@ -429,14 +432,11 @@ void VMAC_Base::VHASH_Update_SSE2(const word64 *data, size_t blocksRemainingInWo
 	AS_POP_IF86(	bp)

 	AS1(	emms)

 #ifdef __GNUC__

-

 	ATT_PREFIX

-

 # if defined(__i386__) || defined(__i686__)

 	// Restore EBX for PIC

 	AS2(	mov 	-20(%%esp), %%ebx)

 # endif

-

 		:

 		: "m" (L1KeyLength), "c" (blocksRemainingInWord64), "S" (data),

 		  "D" (nhK+tagPart*2), "d" (m_isFirstBlock), "a" (polyS+tagPart*4)