+Another example is:
+
+;; X's live range extends beyond the shift, so the register allocator
+;; cannot coalesce it with Y. Because of this, a copy needs to be
+;; emitted before the shift to save the register value before it is
+;; clobbered. However, this copy is not needed if the register
+;; allocator turns the shift into an LEA. This also occurs for ADD.
+
+; Check that the shift gets turned into an LEA.
+; RUN: llvm-upgrade < %s | llvm-as | llc -march=x86 -x86-asm-syntax=intel | \
+; RUN: not grep {mov E.X, E.X}
+
+%G = external global int
+
+int %test1(int %X, int %Y) {
+ %Z = add int %X, %Y
+ volatile store int %Y, int* %G
+ volatile store int %Z, int* %G
+ ret int %X
+}
+
+int %test2(int %X) {
+ %Z = add int %X, 1 ;; inc
+ volatile store int %Z, int* %G
+ ret int %X
+}
+
+//===---------------------------------------------------------------------===//
+
+This:
+#include <xmmintrin.h>
+unsigned test(float f) {
+ return _mm_cvtsi128_si32( (__m128i) _mm_set_ss( f ));
+}
+
+Compiles to:
+_test:
+ movss 4(%esp), %xmm0
+ movd %xmm0, %eax
+ ret
+
+it should compile to a move from the stack slot directly into eax. DAGCombine
+has this xform, but it is currently disabled until the alignment fields of
+the load/store nodes are trustworthy.
+
+//===---------------------------------------------------------------------===//
+
+Sometimes it is better to codegen subtractions from a constant (e.g. 7-x) with
+a neg instead of a sub instruction. Consider:
+
+int test(char X) { return 7-X; }
+
+we currently produce:
+_test:
+ movl $7, %eax
+ movsbl 4(%esp), %ecx
+ subl %ecx, %eax
+ ret
+
+We would use one fewer register if codegen'd as:
+
+ movsbl 4(%esp), %eax
+ neg %eax
+ add $7, %eax
+ ret
+
+Note that this isn't beneficial if the load can be folded into the sub. In
+this case, we want a sub:
+
+int test(int X) { return 7-X; }
+_test:
+ movl $7, %eax
+ subl 4(%esp), %eax
+ ret
+
+//===---------------------------------------------------------------------===//
+
+For code like:
+phi (undef, x)
+
+We get an implicit def on the undef side. If the phi is spilled, we then get:
+implicitdef xmm1
+store xmm1 -> stack
+
+It should be possible to teach the x86 backend to "fold" the store into the
+implicitdef, which just deletes the implicit def.
+
+These instructions should go away:
+#IMPLICIT_DEF %xmm1
+movaps %xmm1, 192(%esp)
+movaps %xmm1, 224(%esp)
+movaps %xmm1, 176(%esp)
+