[dev.link] Merge branch 'master' into dev.link

2 conflicts, that make sense.
	src/cmd/internal/obj/objfile.go
	src/cmd/link/internal/loader/loader.go

Change-Id: Ib224e2d248cb568fa1e888af79dd908b2f5e05ff

1 files changed, 48 insertions, 20 deletions

diff --git a/src/cmd/compile/internal/x86/387.go b/src/cmd/compile/internal/x86/387.go
index 796aa82f19..594adb2cd5 100644
--- a/src/cmd/compile/internal/x86/387.go
+++ b/src/cmd/compile/internal/x86/387.go
@@ -139,12 +139,18 @@ func ssaGenValue387(s *gc.SSAGenState, v *ssa.Value) {
 		// Set precision if needed.  64 bits is the default.
 		switch v.Op {
 		case ssa.Op386ADDSS, ssa.Op386SUBSS, ssa.Op386MULSS, ssa.Op386DIVSS:
-			p := s.Prog(x86.AFSTCW)
+			// Save AX so we can use it as scratch space.
+			p := s.Prog(x86.AMOVL)
+			p.From.Type = obj.TYPE_REG
+			p.From.Reg = x86.REG_AX
 			s.AddrScratch(&p.To)
-			p = s.Prog(x86.AFLDCW)
-			p.From.Type = obj.TYPE_MEM
-			p.From.Name = obj.NAME_EXTERN
-			p.From.Sym = gc.ControlWord32
+			// Install a 32-bit version of the control word.
+			installControlWord(s, gc.ControlWord32, x86.REG_AX)
+			// Restore AX.
+			p = s.Prog(x86.AMOVL)
+			s.AddrScratch(&p.From)
+			p.To.Type = obj.TYPE_REG
+			p.To.Reg = x86.REG_AX
 		}
 
 		var op obj.As
@@ -167,8 +173,7 @@ func ssaGenValue387(s *gc.SSAGenState, v *ssa.Value) {
 		// Restore precision if needed.
 		switch v.Op {
 		case ssa.Op386ADDSS, ssa.Op386SUBSS, ssa.Op386MULSS, ssa.Op386DIVSS:
-			p := s.Prog(x86.AFLDCW)
-			s.AddrScratch(&p.From)
+			restoreControlWord(s)
 		}
 
 	case ssa.Op386UCOMISS, ssa.Op386UCOMISD:
@@ -225,19 +230,11 @@ func ssaGenValue387(s *gc.SSAGenState, v *ssa.Value) {
 	case ssa.Op386CVTTSD2SL, ssa.Op386CVTTSS2SL:
 		push(s, v.Args[0])
 
-		// Save control word.
-		p := s.Prog(x86.AFSTCW)
-		s.AddrScratch(&p.To)
-		p.To.Offset += 4
-
 		// Load control word which truncates (rounds towards zero).
-		p = s.Prog(x86.AFLDCW)
-		p.From.Type = obj.TYPE_MEM
-		p.From.Name = obj.NAME_EXTERN
-		p.From.Sym = gc.ControlWord64trunc
+		installControlWord(s, gc.ControlWord64trunc, v.Reg())
 
 		// Now do the conversion.
-		p = s.Prog(x86.AFMOVLP)
+		p := s.Prog(x86.AFMOVLP)
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = x86.REG_F0
 		s.AddrScratch(&p.To)
@@ -247,9 +244,7 @@ func ssaGenValue387(s *gc.SSAGenState, v *ssa.Value) {
 		p.To.Reg = v.Reg()
 
 		// Restore control word.
-		p = s.Prog(x86.AFLDCW)
-		s.AddrScratch(&p.From)
-		p.From.Offset += 4
+		restoreControlWord(s)
 
 	case ssa.Op386CVTSS2SD:
 		// float32 -> float64 is a nop
@@ -373,3 +368,36 @@ func ssaGenBlock387(s *gc.SSAGenState, b, next *ssa.Block) {
 
 	ssaGenBlock(s, b, next)
 }
+
+// installControlWord saves the current floating-point control
+// word and installs a new one loaded from cw.
+// scratchReg must be an unused register.
+// This call must be paired with restoreControlWord.
+// Bytes 4-5 of the scratch space (s.AddrScratch) are used between
+// this call and restoreControlWord.
+func installControlWord(s *gc.SSAGenState, cw *obj.LSym, scratchReg int16) {
+	// Save current control word.
+	p := s.Prog(x86.AFSTCW)
+	s.AddrScratch(&p.To)
+	p.To.Offset += 4
+
+	// Materialize address of new control word.
+	// Note: this must be a seperate instruction to handle PIE correctly.
+	// See issue 41503.
+	p = s.Prog(x86.ALEAL)
+	p.From.Type = obj.TYPE_MEM
+	p.From.Name = obj.NAME_EXTERN
+	p.From.Sym = cw
+	p.To.Type = obj.TYPE_REG
+	p.To.Reg = scratchReg
+
+	// Load replacement control word.
+	p = s.Prog(x86.AFLDCW)
+	p.From.Type = obj.TYPE_MEM
+	p.From.Reg = scratchReg
+}
+func restoreControlWord(s *gc.SSAGenState) {
+	p := s.Prog(x86.AFLDCW)
+	s.AddrScratch(&p.From)
+	p.From.Offset += 4
+}