1 files changed, 159 insertions, 0 deletions
diff --git a/test/CodeGen/X86/lsr-reuse.ll b/test/CodeGen/X86/lsr-reuse.ll
new file mode 100644
index 0000000000..a1919bab38
--- /dev/null
+++ b/test/CodeGen/X86/lsr-reuse.ll
@@ -0,0 +1,159 @@
+; RUN: llc < %s -march=x86-64 | FileCheck %s
+target datalayout = "e-p:64:64:64"
+target triple = "x86_64-unknown-unknown"
+
+; Full strength reduction reduces register pressure from 5 to 4 here.
+
+; CHECK: full_me:
+; CHECK: movsd   (%rsi), %xmm0
+; CHECK: mulsd   (%rdx), %xmm0
+; CHECK: movsd   %xmm0, (%rdi)
+; CHECK: addq    $8, %rsi
+; CHECK: addq    $8, %rdx
+; CHECK: addq    $8, %rdi
+; CHECK: decq    %rcx
+; CHECK: jne
+
+define void @full_me(double* nocapture %A, double* nocapture %B, double* nocapture %C, i64 %n) nounwind {
+entry:
+  %t0 = icmp sgt i64 %n, 0
+  br i1 %t0, label %loop, label %return
+
+loop:
+  %i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
+  %Ai = getelementptr inbounds double* %A, i64 %i
+  %Bi = getelementptr inbounds double* %B, i64 %i
+  %Ci = getelementptr inbounds double* %C, i64 %i
+  %t1 = load double* %Bi
+  %t2 = load double* %Ci
+  %m = fmul double %t1, %t2
+  store double %m, double* %Ai
+  %i.next = add nsw i64 %i, 1
+  %exitcond = icmp eq i64 %i.next, %n
+  br i1 %exitcond, label %return, label %loop
+
+return:
+  ret void
+}
+
+; In this test, the counting IV exit value is used, so full strength reduction
+; would not reduce register pressure. IndVarSimplify ought to simplify such
+; cases away, but it's useful here to verify that LSR's register pressure
+; heuristics are working as expected.
+
+; CHECK: count_me_0:
+; CHECK: movsd   (%rsi,%rax,8), %xmm0
+; CHECK: mulsd   (%rdx,%rax,8), %xmm0
+; CHECK: movsd   %xmm0, (%rdi,%rax,8)
+; CHECK: incq    %rax
+; CHECK: cmpq    %rax, %rcx
+; CHECK: jne
+
+define i64 @count_me_0(double* nocapture %A, double* nocapture %B, double* nocapture %C, i64 %n) nounwind {
+entry:
+  %t0 = icmp sgt i64 %n, 0
+  br i1 %t0, label %loop, label %return
+
+loop:
+  %i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
+  %Ai = getelementptr inbounds double* %A, i64 %i
+  %Bi = getelementptr inbounds double* %B, i64 %i
+  %Ci = getelementptr inbounds double* %C, i64 %i
+  %t1 = load double* %Bi
+  %t2 = load double* %Ci
+  %m = fmul double %t1, %t2
+  store double %m, double* %Ai
+  %i.next = add nsw i64 %i, 1
+  %exitcond = icmp eq i64 %i.next, %n
+  br i1 %exitcond, label %return, label %loop
+
+return:
+  %q = phi i64 [ 0, %entry ], [ %i.next, %loop ]
+  ret i64 %q
+}
+
+; In this test, the trip count value is used, so full strength reduction
+; would not reduce register pressure.
+; (though it would reduce register pressure inside the loop...)
+
+; CHECK: count_me_1:
+; CHECK: movsd   (%rsi,%rax,8), %xmm0
+; CHECK: mulsd   (%rdx,%rax,8), %xmm0
+; CHECK: movsd   %xmm0, (%rdi,%rax,8)
+; CHECK: incq    %rax
+; CHECK: cmpq    %rax, %rcx
+; CHECK: jne
+
+define i64 @count_me_1(double* nocapture %A, double* nocapture %B, double* nocapture %C, i64 %n) nounwind {
+entry:
+  %t0 = icmp sgt i64 %n, 0
+  br i1 %t0, label %loop, label %return
+
+loop:
+  %i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
+  %Ai = getelementptr inbounds double* %A, i64 %i
+  %Bi = getelementptr inbounds double* %B, i64 %i
+  %Ci = getelementptr inbounds double* %C, i64 %i
+  %t1 = load double* %Bi
+  %t2 = load double* %Ci
+  %m = fmul double %t1, %t2
+  store double %m, double* %Ai
+  %i.next = add nsw i64 %i, 1
+  %exitcond = icmp eq i64 %i.next, %n
+  br i1 %exitcond, label %return, label %loop
+
+return:
+  %q = phi i64 [ 0, %entry ], [ %n, %loop ]
+  ret i64 %q
+}
+
+; This should be fully strength-reduced to reduce register pressure, however
+; the current heuristics get distracted by all the reuse with the stride-1
+; induction variable first.
+
+; But even so, be clever and start the stride-1 variable at a non-zero value
+; to eliminate an in-loop immediate value.
+
+; CHECK: count_me_2:
+; CHECK: movl    $5, %eax
+; CHECK: align
+; CHECK: BB4_1:
+; CHECK: movsd   (%rdi,%rax,8), %xmm0
+; CHECK: addsd   (%rsi,%rax,8), %xmm0
+; CHECK: movsd   %xmm0, (%rdx,%rax,8)
+; CHECK: movsd   40(%rdi,%rax,8), %xmm0
+; CHECK: addsd   40(%rsi,%rax,8), %xmm0
+; CHECK: movsd   %xmm0, 40(%rdx,%rax,8)
+; CHECK: incq    %rax
+; CHECK: cmpq    $5005, %rax
+; CHECK: jne
+
+define void @count_me_2(double* nocapture %A, double* nocapture %B, double* nocapture %C) nounwind {
+entry:
+  br label %loop
+
+loop:
+  %i = phi i64 [ 0, %entry ], [ %i.next, %loop ]
+  %i5 = add i64 %i, 5
+  %Ai = getelementptr double* %A, i64 %i5
+  %t2 = load double* %Ai
+  %Bi = getelementptr double* %B, i64 %i5
+  %t4 = load double* %Bi
+  %t5 = fadd double %t2, %t4
+  %Ci = getelementptr double* %C, i64 %i5
+  store double %t5, double* %Ci
+  %i10 = add i64 %i, 10
+  %Ai10 = getelementptr double* %A, i64 %i10
+  %t9 = load double* %Ai10
+  %Bi10 = getelementptr double* %B, i64 %i10
+  %t11 = load double* %Bi10
+  %t12 = fadd double %t9, %t11
+  %Ci10 = getelementptr double* %C, i64 %i10
+  store double %t12, double* %Ci10
+  %i.next = add i64 %i, 1
+  %exitcond = icmp eq i64 %i.next, 5000
+  br i1 %exitcond, label %return, label %loop
+
+return:
+  ret void
+}