[mips] Make sure loads from lazy-binding entries do not get CSE'd or hoisted out

of loops.

Previously, two consecutive calls to function "func" would result in the
following sequence of instructions:

1. load $16, %got(func)($gp) // load address of lazy-binding stub.
2. move $25, $16
3. jalr $25                  // jump to lazy-binding stub.
4. nop
5. move $25, $16
6. jalr $25                  // jump to lazy-binding stub again.

With this patch, the second call directly jumps to func's address, bypassing
the lazy-binding resolution routine:

1. load $25, %got(func)($gp) // load address of lazy-binding stub.
2. jalr $25                  // jump to lazy-binding stub.
3. nop
4. load $25, %got(func)($gp) // load resolved address of func.
5. jalr $25                  // directly jump to func.

llvm-svn: 191591

4 files changed, 57 insertions, 9 deletions

diff --git a/llvm/test/CodeGen/Mips/brdelayslot.ll b/llvm/test/CodeGen/Mips/brdelayslot.ll
index 869ecd9a839..68341c1ba25 100644
--- a/llvm/test/CodeGen/Mips/brdelayslot.ll
+++ b/llvm/test/CodeGen/Mips/brdelayslot.ll
@@ -160,7 +160,14 @@ for.end:                                          ; preds = %for.body, %entry
 ;
 ; SUCCBB-LABEL:      succbbs_br1:
 ; SUCCBB:      beqz ${{[0-9]+}}, $BB
-; SUCCBB-NEXT: lw $25, %call16(foo100)
+; SUCCBB-NEXT: lw ${{[0-9]+}}, %got(foo101)(${{[0-9]+}})
+
+define internal fastcc void @foo101() {
+entry:
+  tail call void @foo100()
+  tail call void @foo100()
+  ret void
+}
 
 define void @succbbs_br1(i32 %a) {
 entry:
@@ -168,7 +175,7 @@ entry:
   br i1 %tobool, label %if.end, label %if.then
 
 if.then:                                          ; preds = %entry
-  tail call void @foo100() #1
+  tail call fastcc void @foo101()
   br label %if.end
 
 if.end:                                           ; preds = %entry, %if.then
diff --git a/llvm/test/CodeGen/Mips/i64arg.ll b/llvm/test/CodeGen/Mips/i64arg.ll
index 0b16424d94c..b038ad5bf74 100644
--- a/llvm/test/CodeGen/Mips/i64arg.ll
+++ b/llvm/test/CodeGen/Mips/i64arg.ll
@@ -9,11 +9,11 @@ entry:
 ; CHECK: lw  $25, %call16(ff1)
 ; CHECK: jalr
   tail call void @ff1(i32 %i, i64 1085102592623924856) nounwind
-; CHECK: lw $25, %call16(ff2)
-; CHECK: lw $[[R2:[0-9]+]], 80($sp)
-; CHECK: lw $[[R3:[0-9]+]], 84($sp)
-; CHECK: move $4, $[[R2]]
-; CHECK: move $5, $[[R3]]
+; CHECK-DAG: lw $25, %call16(ff2)
+; CHECK-DAG: lw $[[R2:[0-9]+]], 80($sp)
+; CHECK-DAG: lw $[[R3:[0-9]+]], 84($sp)
+; CHECK-DAG: move $4, $[[R2]]
+; CHECK-DAG: move $5, $[[R3]]
 ; CHECK: jalr $25
   tail call void @ff2(i64 %ll, double 3.000000e+00) nounwind
   %sub = add nsw i32 %i, -1
diff --git a/llvm/test/CodeGen/Mips/largeimmprinting.ll b/llvm/test/CodeGen/Mips/largeimmprinting.ll
index 1e96346d1dd..09fee3d9063 100644
--- a/llvm/test/CodeGen/Mips/largeimmprinting.ll
+++ b/llvm/test/CodeGen/Mips/largeimmprinting.ll
@@ -18,11 +18,11 @@ entry:
 ; 64:  dsll  $[[R0]], $[[R0]], 48
 ; 64:  daddiu  $[[R0]], $[[R0]], -1
 ; 64:  dsll  $[[R0]], $[[R0]], 16
-; 64:  daddiu  $[[R0]], $[[R0]], -48
+; 64:  daddiu  $[[R0]], $[[R0]], -32
 ; 64:  daddu $sp, $sp, $[[R0]]
 ; 64:  lui $[[R1:[0-9]+]], 1
 ; 64:  daddu $[[R1]], $sp, $[[R1]]
-; 64:  sd  $ra, 40($[[R1]])
+; 64:  sd  $ra, 24($[[R1]])
 
   %agg.tmp = alloca %struct.S1, align 1
   %tmp = getelementptr inbounds %struct.S1* %agg.tmp, i32 0, i32 0, i32 0
diff --git a/llvm/test/CodeGen/Mips/lazy-binding.ll b/llvm/test/CodeGen/Mips/lazy-binding.ll
new file mode 100644
index 00000000000..839155adad9
--- /dev/null
+++ b/llvm/test/CodeGen/Mips/lazy-binding.ll
@@ -0,0 +1,41 @@
+; RUN: llc -march=mipsel < %s | FileCheck %s
+
+; CHECK-LABEL: foo6:
+; CHECK: %while.body
+; CHECK: lw  $25, %call16(foo2)(${{[0-9]+}})
+; CHECK: jalr $25
+; CHECK: %while.end
+
+define void @foo6(i32 %n) {
+entry:
+  %tobool1 = icmp eq i32 %n, 0
+  br i1 %tobool1, label %while.end, label %while.body
+
+while.body:                                       ; preds = %entry, %while.body
+  %n.addr.02 = phi i32 [ %dec, %while.body ], [ %n, %entry ]
+  %dec = add nsw i32 %n.addr.02, -1
+  tail call void @foo2()
+  %tobool = icmp eq i32 %dec, 0
+  br i1 %tobool, label %while.end, label %while.body
+
+while.end:                                        ; preds = %while.body, %entry
+  ret void
+}
+
+declare void @foo2()
+
+; CHECK-LABEL: foo1:
+; CHECK: lw $25, %call16(foo2)(${{[0-9]+}})
+; CHECK: jalr $25
+; CHECK: lw $25, %call16(foo2)(${{[0-9]+}})
+; CHECK: jalr $25
+; CHECK: lw $25, %call16(foo2)(${{[0-9]+}})
+; CHECK: jalr $25
+
+define void @foo1() {
+entry:
+  tail call void @foo2()
+  tail call void @foo2()
+  tail call void @foo2()
+  ret void
+}