IR, X86: Understand !absolute_symbol metadata on global variables.

Summary:
Attaching !absolute_symbol to a global variable does two things:
1) Marks it as an absolute symbol reference.
2) Specifies the value range of that symbol's address.
Teach the X86 backend to allow absolute symbols to appear in place of
immediates by extending the relocImm and mov64imm32 matchers. Start using
relocImm in more places where it is legal.

As previously proposed on llvm-dev:
http://lists.llvm.org/pipermail/llvm-dev/2016-October/105800.html

Differential Revision: https://reviews.llvm.org/D25878

llvm-svn: 289087

5 files changed, 177 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/X86/absolute-bit-mask.ll b/llvm/test/CodeGen/X86/absolute-bit-mask.ll
new file mode 100644
index 00000000000..6e119494ac3
--- /dev/null
+++ b/llvm/test/CodeGen/X86/absolute-bit-mask.ll
@@ -0,0 +1,61 @@
+; RUN: llc < %s | FileCheck %s
+; RUN: llc -relocation-model=pic < %s | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@bit_mask8 = external hidden global i8, !absolute_symbol !0
+@bit_mask32 = external hidden global i8, !absolute_symbol !1
+@bit_mask64 = external hidden global i8, !absolute_symbol !2
+
+declare void @f()
+
+define void @foo8(i8* %ptr) {
+  %load = load i8, i8* %ptr
+  ; CHECK: testb $bit_mask8, (%rdi)
+  %and = and i8 %load, ptrtoint (i8* @bit_mask8 to i8)
+  %icmp = icmp eq i8 %and, 0
+  br i1 %icmp, label %t, label %f
+
+t:
+  call void @f()
+  ret void
+
+f:
+  ret void
+}
+
+define void @foo32(i32* %ptr) {
+  %load = load i32, i32* %ptr
+  ; CHECK: testl $bit_mask32, (%rdi)
+  %and = and i32 %load, ptrtoint (i8* @bit_mask32 to i32)
+  %icmp = icmp eq i32 %and, 0
+  br i1 %icmp, label %t, label %f
+
+t:
+  call void @f()
+  ret void
+
+f:
+  ret void
+}
+
+define void @foo64(i64* %ptr) {
+  %load = load i64, i64* %ptr
+  ; CHECK: movabsq $bit_mask64, %rax
+  ; CHECK: testq (%rdi), %rax
+  %and = and i64 %load, ptrtoint (i8* @bit_mask64 to i64)
+  %icmp = icmp eq i64 %and, 0
+  br i1 %icmp, label %t, label %f
+
+t:
+  call void @f()
+  ret void
+
+f:
+  ret void
+}
+
+!0 = !{i64 0, i64 256}
+!1 = !{i64 0, i64 4294967296}
+!2 = !{i64 -1, i64 -1}
diff --git a/llvm/test/CodeGen/X86/absolute-bt.ll b/llvm/test/CodeGen/X86/absolute-bt.ll
new file mode 100644
index 00000000000..ffc16bc62ee
--- /dev/null
+++ b/llvm/test/CodeGen/X86/absolute-bt.ll
@@ -0,0 +1,51 @@
+; RUN: llc < %s | FileCheck %s
+; RUN: llc -relocation-model=pic < %s | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@bit_mask8 = external hidden global i8, !absolute_symbol !0
+@bit_mask32 = external hidden global i8, !absolute_symbol !1
+@bit_mask64 = external hidden global i8, !absolute_symbol !2
+
+declare void @f()
+
+define void @foo32(i32* %ptr) {
+  %load = load i32, i32* %ptr
+  %and = and i32 %load, 31
+  %shl = shl i32 1, %and
+  %and2 = and i32 %shl, ptrtoint (i8* @bit_mask32 to i32)
+  ; CHECK: movl $bit_mask32, %eax
+  ; CHECK: btl %ecx, %eax
+  %icmp = icmp eq i32 %and2, 0
+  br i1 %icmp, label %t, label %f
+
+t:
+  call void @f()
+  ret void
+
+f:
+  ret void
+}
+
+define void @foo64(i64* %ptr) {
+  %load = load i64, i64* %ptr
+  %and = and i64 %load, 63
+  %shl = shl i64 1, %and
+  %and2 = and i64 %shl, ptrtoint (i8* @bit_mask64 to i64)
+  ; CHECK: movabsq $bit_mask64, %rax
+  ; CHECK: btq %rcx, %rax
+  %icmp = icmp eq i64 %and2, 0
+  br i1 %icmp, label %t, label %f
+
+t:
+  call void @f()
+  ret void
+
+f:
+  ret void
+}
+
+!0 = !{i64 0, i64 256}
+!1 = !{i64 0, i64 4294967296}
+!2 = !{i64 -1, i64 -1}
diff --git a/llvm/test/CodeGen/X86/absolute-constant.ll b/llvm/test/CodeGen/X86/absolute-constant.ll
new file mode 100644
index 00000000000..d93fb276c8e
--- /dev/null
+++ b/llvm/test/CodeGen/X86/absolute-constant.ll
@@ -0,0 +1,28 @@
+; RUN: llc < %s | FileCheck %s
+; RUN: llc -relocation-model=pic < %s | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@foo = external global i8, align 1, !absolute_symbol !0
+
+define void @bar(i8* %x) {
+entry:
+  %0 = load i8, i8* %x, align 1
+  %conv = sext i8 %0 to i32
+  ; CHECK: testb $foo, (%rdi)
+  %and = and i32 %conv, sext (i8 ptrtoint (i8* @foo to i8) to i32)
+  %tobool = icmp eq i32 %and, 0
+  br i1 %tobool, label %if.end, label %if.then
+
+if.then:                                          ; preds = %entry
+  tail call void (...) @xf()
+  br label %if.end
+
+if.end:                                           ; preds = %entry, %if.then
+  ret void
+}
+
+declare void @xf(...)
+
+!0 = !{i32 0, i32 256}
diff --git a/llvm/test/CodeGen/X86/absolute-rotate.ll b/llvm/test/CodeGen/X86/absolute-rotate.ll
new file mode 100644
index 00000000000..c0ecb82adc2
--- /dev/null
+++ b/llvm/test/CodeGen/X86/absolute-rotate.ll
@@ -0,0 +1,27 @@
+; RUN: llc < %s | FileCheck %s
+; RUN: llc -relocation-model=pic < %s | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@align = external hidden global i8, !absolute_symbol !0
+
+declare void @f()
+
+define void @foo(i64 %val) {
+  %shr = lshr i64 %val, zext (i8 ptrtoint (i8* @align to i8) to i64)
+  %shl = shl i64 %val, zext (i8 sub (i8 64, i8 ptrtoint (i8* @align to i8)) to i64)
+  ; CHECK: rorq $align, %rdi
+  %ror = or i64 %shr, %shl
+  %cmp = icmp ult i64 %ror, 109
+  br i1 %cmp, label %t, label %f
+
+t:
+  call void @f()
+  ret void
+
+f:
+  ret void
+}
+
+!0 = !{i64 0, i64 256}
diff --git a/llvm/test/Transforms/FunctionAttrs/nonnull-global.ll b/llvm/test/Transforms/FunctionAttrs/nonnull-global.ll
new file mode 100644
index 00000000000..43353e82270
--- /dev/null
+++ b/llvm/test/Transforms/FunctionAttrs/nonnull-global.ll
@@ -0,0 +1,10 @@
+; RUN: opt -S -functionattrs %s | FileCheck %s
+
+@a = external global i8, !absolute_symbol !0
+
+; CHECK-NOT: define nonnull
+define i8* @foo() {
+  ret i8* @a
+}
+
+!0 = !{i64 0, i64 256}