add a testcase

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45768 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/X86/README.txt

@@ -1601,13 +1601,13 @@ This would result in smaller code and more efficient microops.
 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 @@ the neg/abs instruction, turning it into an *integer* operation, like this:
 	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;
+}
 
 //===---------------------------------------------------------------------===//

lib/Target/X86/X86InstrInfo.cpp

@@ -1740,8 +1740,7 @@ X86InstrInfo::foldMemoryOperand(MachineInstr *MI, unsigned i,
   
   // 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,
 }
 
 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 @@ MachineInstr* X86InstrInfo::foldMemoryOperand(MachineInstr *MI,
 
 
 bool X86InstrInfo::canFoldMemoryOperand(MachineInstr *MI,
-                                         SmallVectorImpl<unsigned> &Ops) const {
+                                        SmallVectorImpl<unsigned> &Ops) const {
   // Check switch flag 
   if (NoFusing) return 0;