[llvm-commits] [llvm] r45768 - in /llvm/trunk/lib/Target/X86: README.txt X86InstrInfo.cpp

[Chris Lattner]

Author: lattner
Date: Tue Jan  8 18:37:18 2008
New Revision: 45768

URL: http://llvm.org/viewvc/llvm-project?rev=45768&view=rev
Log:
add a testcase 

Modified:
    llvm/trunk/lib/Target/X86/README.txt
    llvm/trunk/lib/Target/X86/X86InstrInfo.cpp

Modified: llvm/trunk/lib/Target/X86/README.txt
URL: 
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/README.txt?rev=45768&r1=45767&r2=45768&view=diff

==============================================================================
--- llvm/trunk/lib/Target/X86/README.txt (original)
+++ llvm/trunk/lib/Target/X86/README.txt Tue Jan  8 18:37:18 2008
@@ -1601,13 +1601,13 @@
 In SSE mode, we turn abs and neg into a load from the constant pool plus a xor
 or and instruction, for example:
 
-       xorpd   LCPI2_0-"L2$pb"(%esi), %xmm2
+       xorpd   LCPI1_0, %xmm2
 
 However, if xmm2 gets spilled, we end up with really ugly code like this:
 
-       %xmm2 = reload [mem]
-       xorpd   LCPI2_0-"L2$pb"(%esi), %xmm2
-       store %xmm2 -> [mem]
+       movsd   (%esp), %xmm0
+       xorpd   LCPI1_0, %xmm0
+       movsd   %xmm0, (%esp)
 
 Since we 'know' that this is a 'neg', we can actually "fold" the spill into
 the neg/abs instruction, turning it into an *integer* operation, like this:
@@ -1615,6 +1615,17 @@
        xorl 2147483648, [mem+4]     ## 2147483648 = (1 << 31)
 
 you could also use xorb, but xorl is less likely to lead to a partial register
-stall.
+stall.  Here is a contrived testcase:
+
+double a, b, c;
+void test(double *P) {
+  double X = *P;
+  a = X;
+  bar();
+  X = -X;
+  b = X;
+  bar();
+  c = X;
+}
 
 //===---------------------------------------------------------------------===//

Modified: llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
URL: 
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86InstrInfo.cpp?rev=45768&r1=45767&r2=45768&view=diff

==============================================================================
--- llvm/trunk/lib/Target/X86/X86InstrInfo.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86InstrInfo.cpp Tue Jan  8 18:37:18 2008
@@ -1740,8 +1740,7 @@
   
   // No fusion 
   if (PrintFailedFusing)
-    cerr << "We failed to fuse ("
-         << ((i == 1) ? "r" : "s") << "): " << *MI;
+    cerr << "We failed to fuse operand " << i << *MI;
   return NULL;
 }
 
@@ -1773,8 +1772,8 @@
 }
 
 MachineInstr* X86InstrInfo::foldMemoryOperand(MachineInstr *MI,
-                                                 SmallVectorImpl<unsigned> 
&Ops,
-                                                 MachineInstr *LoadMI) const {
+                                              SmallVectorImpl<unsigned> &Ops,
+                                              MachineInstr *LoadMI) const {
   // Check switch flag 
   if (NoFusing) return NULL;
 
@@ -1802,7 +1801,7 @@
 
 
 bool X86InstrInfo::canFoldMemoryOperand(MachineInstr *MI,
-                                         SmallVectorImpl<unsigned> &Ops) const 
{
+                                        SmallVectorImpl<unsigned> &Ops) const {
   // Check switch flag 
   if (NoFusing) return 0;
 


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