[llvm] r212795 - [X86] AVX512: Improve readability of isCDisp8

[Adam Nemet]

Author: anemet
Date: Fri Jul 11 00:23:25 2014
New Revision: 212795

URL: http://llvm.org/viewvc/llvm-project?rev=212795&view=rev
Log:
[X86] AVX512: Improve readability of isCDisp8

No functional change.  As I was trying to understand this function, I found
that variables were reused with confusing names and the broadcast case was a
bit too implicit.  Hopefully, this is an improvement.

Modified:
    llvm/trunk/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp

Modified: llvm/trunk/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp?rev=212795&r1=212794&r2=212795&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp (original)
+++ llvm/trunk/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp Fri Jul 11 00:23:25 2014
@@ -197,14 +197,23 @@ static bool isCDisp8(uint64_t TSFlags, i
     return isDisp8(Value);
   }
 
-  unsigned MemObjSize = 1U << CD8E;
+  unsigned ElemSize = 1U << CD8E;
+  unsigned MemObjSize;
+  // The unit of displacement is either
+  //   - the size of a  power-of-two number of elements or
+  //   - the size of a single element for broadcasts or
+  //   - the total vector size divided by a power-of-two number.
   if (CD8V & 4) {
     // Fixed vector length
-    MemObjSize *= 1U << (CD8V & 0x3);
+    unsigned NumElems = 1U << (CD8V & 0x3);
+    MemObjSize = ElemSize * NumElems;
   } else {
     // Modified vector length
     bool EVEX_b = (TSFlags >> X86II::VEXShift) & X86II::EVEX_B;
-    if (!EVEX_b) {
+    if (EVEX_b)
+      // Broadcast implies element size units.
+      MemObjSize = ElemSize;
+    else {
       unsigned EVEX_LL = ((TSFlags >> X86II::VEXShift) & X86II::VEX_L) ? 1 : 0;
       EVEX_LL += ((TSFlags >> X86II::VEXShift) & X86II::EVEX_L2) ? 2 : 0;
       assert(EVEX_LL < 3 && "");