When x86 addresses matching exceeds its recursion limit, check to

see if the base register is already occupied before assuming it can be
used. This fixes bogus code generation in the accompanying testcase.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41049 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 47 insertions, 0 deletions

diff --git a/test/CodeGen/X86/lea-recursion.ll b/test/CodeGen/X86/lea-recursion.ll
new file mode 100644
index 0000000..ca7b367
--- /dev/null
+++ b/test/CodeGen/X86/lea-recursion.ll
@@ -0,0 +1,47 @@
+; RUN: llvm-as < %s | llc -march=x86-64 | grep lea | wc -l | grep 12
+
+; This testcase was written to demonstrate an instruction-selection problem,
+; however it also happens to expose a limitation in the DAGCombiner's
+; expression reassociation which causes it to miss opportunities for
+; constant folding due to the intermediate adds having multiple uses.
+; The Reassociate pass has similar limitations. If these limitations are
+; fixed, the test commands above will need to be updated to expect fewer
+; lea instructions.
+
+@g0 = weak global [1000 x i32] zeroinitializer, align 32		; <[1000 x i32]*> [#uses=8]
+@g1 = weak global [1000 x i32] zeroinitializer, align 32		; <[1000 x i32]*> [#uses=7]
+
+define void @foo() {
+entry:
+	%tmp4 = load i32* getelementptr ([1000 x i32]* @g0, i32 0, i32 0)		; <i32> [#uses=1]
+	%tmp8 = load i32* getelementptr ([1000 x i32]* @g1, i32 0, i32 0)		; <i32> [#uses=1]
+	%tmp9 = add i32 %tmp4, 1		; <i32> [#uses=1]
+	%tmp10 = add i32 %tmp9, %tmp8		; <i32> [#uses=2]
+	store i32 %tmp10, i32* getelementptr ([1000 x i32]* @g0, i32 0, i32 1)
+	%tmp8.1 = load i32* getelementptr ([1000 x i32]* @g1, i32 0, i32 1)		; <i32> [#uses=1]
+	%tmp9.1 = add i32 %tmp10, 1		; <i32> [#uses=1]
+	%tmp10.1 = add i32 %tmp9.1, %tmp8.1		; <i32> [#uses=2]
+	store i32 %tmp10.1, i32* getelementptr ([1000 x i32]* @g0, i32 0, i32 2)
+	%tmp8.2 = load i32* getelementptr ([1000 x i32]* @g1, i32 0, i32 2)		; <i32> [#uses=1]
+	%tmp9.2 = add i32 %tmp10.1, 1		; <i32> [#uses=1]
+	%tmp10.2 = add i32 %tmp9.2, %tmp8.2		; <i32> [#uses=2]
+	store i32 %tmp10.2, i32* getelementptr ([1000 x i32]* @g0, i32 0, i32 3)
+	%tmp8.3 = load i32* getelementptr ([1000 x i32]* @g1, i32 0, i32 3)		; <i32> [#uses=1]
+	%tmp9.3 = add i32 %tmp10.2, 1		; <i32> [#uses=1]
+	%tmp10.3 = add i32 %tmp9.3, %tmp8.3		; <i32> [#uses=2]
+	store i32 %tmp10.3, i32* getelementptr ([1000 x i32]* @g0, i32 0, i32 4)
+	%tmp8.4 = load i32* getelementptr ([1000 x i32]* @g1, i32 0, i32 4)		; <i32> [#uses=1]
+	%tmp9.4 = add i32 %tmp10.3, 1		; <i32> [#uses=1]
+	%tmp10.4 = add i32 %tmp9.4, %tmp8.4		; <i32> [#uses=2]
+	store i32 %tmp10.4, i32* getelementptr ([1000 x i32]* @g0, i32 0, i32 5)
+	%tmp8.5 = load i32* getelementptr ([1000 x i32]* @g1, i32 0, i32 5)		; <i32> [#uses=1]
+	%tmp9.5 = add i32 %tmp10.4, 1		; <i32> [#uses=1]
+	%tmp10.5 = add i32 %tmp9.5, %tmp8.5		; <i32> [#uses=2]
+	store i32 %tmp10.5, i32* getelementptr ([1000 x i32]* @g0, i32 0, i32 6)
+	%tmp8.6 = load i32* getelementptr ([1000 x i32]* @g1, i32 0, i32 6)		; <i32> [#uses=1]
+	%tmp9.6 = add i32 %tmp10.5, 1		; <i32> [#uses=1]
+	%tmp10.6 = add i32 %tmp9.6, %tmp8.6		; <i32> [#uses=1]
+	store i32 %tmp10.6, i32* getelementptr ([1000 x i32]* @g0, i32 0, i32 7)
+	ret void
+}
+