If a loop termination compare instruction is the only use of its stride,
and the compaison is against a constant value, try eliminate the stride
by moving the compare instruction to another stride and change its
constant operand accordingly. e.g.
loop:
...
v1 = v1 + 3
v2 = v2 + 1
if (v2 < 10) goto loop
=>
loop:
...
v1 = v1 + 3
if (v1 < 30) goto loop
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@43336 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/CodeGen/X86/loop-strength-reduce4.ll b/test/CodeGen/X86/loop-strength-reduce4.ll
new file mode 100644
index 0000000..711f223
--- /dev/null
+++ b/test/CodeGen/X86/loop-strength-reduce4.ll
@@ -0,0 +1,49 @@
+; RUN: llvm-as < %s | llc -march=x86 | grep cmp | grep 64
+; RUN: llvm-as < %s | llc -march=x86 | not grep inc
+
+@state = external global [0 x i32] ; <[0 x i32]*> [#uses=4]
+@S = external global [0 x i32] ; <[0 x i32]*> [#uses=4]
+
+define i32 @foo() {
+entry:
+ br label %bb
+
+bb: ; preds = %bb, %entry
+ %indvar = phi i32 [ 0, %entry ], [ %indvar.next, %bb ] ; <i32> [#uses=2]
+ %t.063.0 = phi i32 [ 0, %entry ], [ %tmp47, %bb ] ; <i32> [#uses=1]
+ %j.065.0 = shl i32 %indvar, 2 ; <i32> [#uses=4]
+ %tmp3 = getelementptr [0 x i32]* @state, i32 0, i32 %j.065.0 ; <i32*> [#uses=2]
+ %tmp4 = load i32* %tmp3, align 4 ; <i32> [#uses=1]
+ %tmp6 = getelementptr [0 x i32]* @S, i32 0, i32 %t.063.0 ; <i32*> [#uses=1]
+ %tmp7 = load i32* %tmp6, align 4 ; <i32> [#uses=1]
+ %tmp8 = xor i32 %tmp7, %tmp4 ; <i32> [#uses=2]
+ store i32 %tmp8, i32* %tmp3, align 4
+ %tmp1378 = or i32 %j.065.0, 1 ; <i32> [#uses=1]
+ %tmp16 = getelementptr [0 x i32]* @state, i32 0, i32 %tmp1378 ; <i32*> [#uses=2]
+ %tmp17 = load i32* %tmp16, align 4 ; <i32> [#uses=1]
+ %tmp19 = getelementptr [0 x i32]* @S, i32 0, i32 %tmp8 ; <i32*> [#uses=1]
+ %tmp20 = load i32* %tmp19, align 4 ; <i32> [#uses=1]
+ %tmp21 = xor i32 %tmp20, %tmp17 ; <i32> [#uses=2]
+ store i32 %tmp21, i32* %tmp16, align 4
+ %tmp2680 = or i32 %j.065.0, 2 ; <i32> [#uses=1]
+ %tmp29 = getelementptr [0 x i32]* @state, i32 0, i32 %tmp2680 ; <i32*> [#uses=2]
+ %tmp30 = load i32* %tmp29, align 4 ; <i32> [#uses=1]
+ %tmp32 = getelementptr [0 x i32]* @S, i32 0, i32 %tmp21 ; <i32*> [#uses=1]
+ %tmp33 = load i32* %tmp32, align 4 ; <i32> [#uses=1]
+ %tmp34 = xor i32 %tmp33, %tmp30 ; <i32> [#uses=2]
+ store i32 %tmp34, i32* %tmp29, align 4
+ %tmp3982 = or i32 %j.065.0, 3 ; <i32> [#uses=1]
+ %tmp42 = getelementptr [0 x i32]* @state, i32 0, i32 %tmp3982 ; <i32*> [#uses=2]
+ %tmp43 = load i32* %tmp42, align 4 ; <i32> [#uses=1]
+ %tmp45 = getelementptr [0 x i32]* @S, i32 0, i32 %tmp34 ; <i32*> [#uses=1]
+ %tmp46 = load i32* %tmp45, align 4 ; <i32> [#uses=1]
+ %tmp47 = xor i32 %tmp46, %tmp43 ; <i32> [#uses=3]
+ store i32 %tmp47, i32* %tmp42, align 4
+ %indvar.next = add i32 %indvar, 1 ; <i32> [#uses=2]
+ %exitcond = icmp eq i32 %indvar.next, 4 ; <i1> [#uses=1]
+ br i1 %exitcond, label %bb57, label %bb
+
+bb57: ; preds = %bb
+ %tmp59 = and i32 %tmp47, 255 ; <i32> [#uses=1]
+ ret i32 %tmp59
+}