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-reduce3.ll b/test/CodeGen/X86/loop-strength-reduce3.ll
new file mode 100644
index 0000000..4e95bdd
--- /dev/null
+++ b/test/CodeGen/X86/loop-strength-reduce3.ll
@@ -0,0 +1,37 @@
+; RUN: llvm-as < %s | llc -march=x86 | grep cmp | grep 240
+; RUN: llvm-as < %s | llc -march=x86 | grep inc | count 1
+
+define i32 @foo(i32 %A, i32 %B, i32 %C, i32 %D) {
+entry:
+ %tmp2955 = icmp sgt i32 %C, 0 ; <i1> [#uses=1]
+ br i1 %tmp2955, label %bb26.outer.us, label %bb40.split
+
+bb26.outer.us: ; preds = %bb26.bb32_crit_edge.us, %entry
+ %i.044.0.ph.us = phi i32 [ 0, %entry ], [ %indvar.next57, %bb26.bb32_crit_edge.us ] ; <i32> [#uses=2]
+ %k.1.ph.us = phi i32 [ 0, %entry ], [ %k.0.us, %bb26.bb32_crit_edge.us ] ; <i32> [#uses=1]
+ %tmp3.us = mul i32 %i.044.0.ph.us, 6 ; <i32> [#uses=1]
+ br label %bb1.us
+
+bb1.us: ; preds = %bb1.us, %bb26.outer.us
+ %j.053.us = phi i32 [ 0, %bb26.outer.us ], [ %tmp25.us, %bb1.us ] ; <i32> [#uses=2]
+ %k.154.us = phi i32 [ %k.1.ph.us, %bb26.outer.us ], [ %k.0.us, %bb1.us ] ; <i32> [#uses=1]
+ %tmp5.us = add i32 %tmp3.us, %j.053.us ; <i32> [#uses=1]
+ %tmp7.us = shl i32 %D, %tmp5.us ; <i32> [#uses=2]
+ %tmp9.us = icmp eq i32 %tmp7.us, %B ; <i1> [#uses=1]
+ %tmp910.us = zext i1 %tmp9.us to i32 ; <i32> [#uses=1]
+ %tmp12.us = and i32 %tmp7.us, %A ; <i32> [#uses=1]
+ %tmp19.us = and i32 %tmp12.us, %tmp910.us ; <i32> [#uses=1]
+ %k.0.us = add i32 %tmp19.us, %k.154.us ; <i32> [#uses=3]
+ %tmp25.us = add i32 %j.053.us, 1 ; <i32> [#uses=2]
+ %tmp29.us = icmp slt i32 %tmp25.us, %C ; <i1> [#uses=1]
+ br i1 %tmp29.us, label %bb1.us, label %bb26.bb32_crit_edge.us
+
+bb26.bb32_crit_edge.us: ; preds = %bb1.us
+ %indvar.next57 = add i32 %i.044.0.ph.us, 1 ; <i32> [#uses=2]
+ %exitcond = icmp eq i32 %indvar.next57, 40 ; <i1> [#uses=1]
+ br i1 %exitcond, label %bb40.split, label %bb26.outer.us
+
+bb40.split: ; preds = %bb26.bb32_crit_edge.us, %entry
+ %k.1.lcssa.lcssa.us-lcssa = phi i32 [ %k.0.us, %bb26.bb32_crit_edge.us ], [ 0, %entry ] ; <i32> [#uses=1]
+ ret i32 %k.1.lcssa.lcssa.us-lcssa
+}