Codegen this:
int %foo(int %X) {
%T = add int %X, 13
%S = mul int %T, 3
ret int %S
}
as this:
mov %ECX, DWORD PTR [%ESP + 4]
lea %EAX, DWORD PTR [%ECX + 2*%ECX + 39]
ret
instead of this:
mov %ECX, DWORD PTR [%ESP + 4]
mov %EAX, %ECX
add %EAX, 13
imul %EAX, %EAX, 3
ret
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@19633 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelPattern.cpp b/lib/Target/X86/X86ISelPattern.cpp
index 7a623e5..5f98524 100644
--- a/lib/Target/X86/X86ISelPattern.cpp
+++ b/lib/Target/X86/X86ISelPattern.cpp
@@ -1636,6 +1636,24 @@
}
}
+ // Fold common multiplies into LEA instructions.
+ if (Node->getOpcode() == ISD::MUL && N.getValueType() == MVT::i32) {
+ switch ((int)CN->getValue()) {
+ default: break;
+ case 3:
+ case 5:
+ case 9:
+ X86AddressMode AM;
+ // Remove N from exprmap so SelectAddress doesn't get confused.
+ ExprMap.erase(N);
+ SelectAddress(N, AM);
+ // Restore it to the map.
+ ExprMap[N] = Result;
+ addFullAddress(BuildMI(BB, X86::LEA32r, 4, Result), AM);
+ return Result;
+ }
+ }
+
switch (N.getValueType()) {
default: assert(0 && "Cannot xor this type!");
case MVT::i1: