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

1 files changed, 37 insertions, 0 deletions

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
+}