On x86 favors folding short immediate into some arithmetic operations (e.g. add, and, xor, etc.) because materializing an immediate in a register is expensive in turns of code size.

e.g.
movl 4(%esp), %eax
addl $4, %eax

is 2 bytes shorter than

movl $4, %eax
addl 4(%esp), %eax


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60139 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 0 deletions

diff --git a/test/CodeGen/X86/fold-imm.ll b/test/CodeGen/X86/fold-imm.ll
new file mode 100644
index 0000000000..1623f31d74
--- /dev/null
+++ b/test/CodeGen/X86/fold-imm.ll
@@ -0,0 +1,14 @@
+; RUN: llvm-as < %s | llc -march=x86 | grep inc
+; RUN: llvm-as < %s | llc -march=x86 | grep add | grep 4
+
+define i32 @test(i32 %X) nounwind {
+entry:
+	%0 = add i32 %X, 1
+	ret i32 %0
+}
+
+define i32 @test2(i32 %X) nounwind {
+entry:
+	%0 = add i32 %X, 4
+	ret i32 %0
+}