[ARM] Mark LEApcrel instructions as isAsCheapAsAMove

Doing this means that if an LEApcrel is used in two places we will rematerialize
instead of generating two MOVs. This is particularly useful for printfs using
the same format string, where we want to generate an address into a register
that's going to get corrupted by the call.

Differential Revision: https://reviews.llvm.org/D32858

llvm-svn: 303054

5 files changed, 33 insertions, 4 deletions

diff --git a/llvm/lib/Target/ARM/ARMInstrInfo.td b/llvm/lib/Target/ARM/ARMInstrInfo.td
index 9e33f5ced87..5b7666af876 100644
--- a/llvm/lib/Target/ARM/ARMInstrInfo.td
+++ b/llvm/lib/Target/ARM/ARMInstrInfo.td
@@ -2222,7 +2222,7 @@ def ADR : AI1<{0,?,?,0}, (outs GPR:$Rd), (ins adrlabel:$label),
   let Inst{11-0} = label{11-0};
 }
 
-let hasSideEffects = 0, isReMaterializable = 1 in
+let hasSideEffects = 0, isReMaterializable = 1, isAsCheapAsAMove = 1 in
 def LEApcrel : ARMPseudoInst<(outs GPR:$Rd), (ins i32imm:$label, pred:$p),
                     4, IIC_iALUi, []>, Sched<[WriteALU, ReadALU]>;
 
diff --git a/llvm/lib/Target/ARM/ARMInstrThumb.td b/llvm/lib/Target/ARM/ARMInstrThumb.td
index bee83dfb6f6..118627fd5d7 100644
--- a/llvm/lib/Target/ARM/ARMInstrThumb.td
+++ b/llvm/lib/Target/ARM/ARMInstrThumb.td
@@ -1402,7 +1402,7 @@ def tADR : T1I<(outs tGPR:$Rd), (ins t_adrlabel:$addr, pred:$p),
   let DecoderMethod = "DecodeThumbAddSpecialReg";
 }
 
-let hasSideEffects = 0, isReMaterializable = 1 in
+let hasSideEffects = 0, isReMaterializable = 1, isAsCheapAsAMove = 1 in
 def tLEApcrel   : tPseudoInst<(outs tGPR:$Rd), (ins i32imm:$label, pred:$p),
                               2, IIC_iALUi, []>, Sched<[WriteALU]>;
 
diff --git a/llvm/lib/Target/ARM/ARMInstrThumb2.td b/llvm/lib/Target/ARM/ARMInstrThumb2.td
index bf3d820e7b7..842c46cc2b6 100644
--- a/llvm/lib/Target/ARM/ARMInstrThumb2.td
+++ b/llvm/lib/Target/ARM/ARMInstrThumb2.td
@@ -1227,7 +1227,7 @@ def t2ADR : T2PCOneRegImm<(outs rGPR:$Rd),
   let DecoderMethod = "DecodeT2Adr";
 }
 
-let hasSideEffects = 0, isReMaterializable = 1 in
+let hasSideEffects = 0, isReMaterializable = 1, isAsCheapAsAMove = 1 in
 def t2LEApcrel   : t2PseudoInst<(outs rGPR:$Rd), (ins i32imm:$label, pred:$p),
                                 4, IIC_iALUi, []>, Sched<[WriteALU, ReadALU]>;
 let hasSideEffects = 1 in
diff --git a/llvm/test/CodeGen/ARM/adr-remat.ll b/llvm/test/CodeGen/ARM/adr-remat.ll
new file mode 100644
index 00000000000..15d7f9cb8db
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/adr-remat.ll
@@ -0,0 +1,25 @@
+; RUN: llc -mtriple=armv7a   %s -o - | FileCheck %s
+; RUN: llc -mtriple=thumbv7m %s -o - | FileCheck %s
+; RUN: llc -mtriple=thumbv6m %s -o - | FileCheck %s
+
+@str.1 = private unnamed_addr constant [58 x i8] c"+-------------------------------------------------------+\00"
+@str.2 = private unnamed_addr constant [58 x i8] c"|                                                       |\00"
+
+declare i32 @puts(i8* nocapture readonly)
+
+; Check that we rematerialize the adr of str.1 instead of doing one adr and two
+; movs.
+
+; CHECK: adr r0, [[STR1:.LCPI[0-9]+_[0-9]+]]
+; CHECK: bl puts
+; CHECK: adr r0, {{.LCPI[0-9]+_[0-9]+}}
+; CHECK: bl puts
+; CHECK: adr r0, [[STR1]]
+; CHECK: b{{l?}} puts
+define void @fn() {
+entry:
+  %puts1 = tail call i32 @puts(i8* getelementptr inbounds ([58 x i8], [58 x i8]* @str.1, i32 0, i32 0))
+  %puts2 = tail call i32 @puts(i8* getelementptr inbounds ([58 x i8], [58 x i8]* @str.2, i32 0, i32 0))
+  %puts3 = tail call i32 @puts(i8* getelementptr inbounds ([58 x i8], [58 x i8]* @str.1, i32 0, i32 0))
+  ret void
+}
diff --git a/llvm/test/CodeGen/ARM/align-sp-adjustment.ll b/llvm/test/CodeGen/ARM/align-sp-adjustment.ll
index cce7b03e236..091279e75a2 100644
--- a/llvm/test/CodeGen/ARM/align-sp-adjustment.ll
+++ b/llvm/test/CodeGen/ARM/align-sp-adjustment.ll
@@ -1,6 +1,10 @@
 ; RUN: llc -mtriple=thumbv7 -o - %s | FileCheck %s
 
-; CHECK: [sp, #2120]
+; p5 will have been pushed to the stack. Check that it's correctly aligned by
+; looking at the offset of the instruction that loads it. Note that this is
+; very fragile and this test may need to be updated if we happen to spill more
+; or less to the stack.
+; CHECK: ldr{{(.w)?}} r{{[0-9]+}}, [sp, #2104]
 
 %struct.struct_2 = type { [172 x %struct.struct_1] }
 %struct.struct_1 = type { i32, i32, i32 }